Syd fell first, but Carmy fell harder, and here's why:
To cut an already too-long analysis short, like most people, the moment that convinced me that Syd and Carmy are not platonic, was when she came back to the restaurant at the end of Season 1. However, I have mostly seen that scene discussed from Carmy's perspective, i.e., no one's platonic colleagues look at us the way Carmy looks at Syd. As a result, a common take I've seen is that he is potentially more into Syd than she is into him. I wholeheartedly disagree with that take. Not only do I think Syd is just into him, but she also fell for him first. To me, the bigger moment in the finale was about the fact that Syd chose to come back to the Beef at all.
When she left the restaurant, she wasn't the only one who had reached their boiling point. Carmy was also trash to Marcus and the others, but the next day, they all came back for various implied reasons. For example, Marcus returns because he recognises Carmy as the real deal, especially after Sydney tells him about the hamachi. He, Marcus, also realises that Carmy is a very rare opportunity; there aren't many high-end chefs who'll invest the kind of (unpaid) training that Carmy has been doing. So on his own, without Carmy reaching out or even apologising to him, Marcus chooses to come back. Sydney, on the other hand, does not. Even though she applied to the Beef for the exact same reasons that Marcus chooses to stay.
But then Carmy gets the letter from Mikey. The letter, in my opinion, serves as a multipurpose device that moves the story forward in the following ways. Firstly, it gives Carmy the much-needed "sign" he's been looking for from his brother. Something to let him know that even though the Beef is a mess and Carmy is making way too many mistakes, Mikey would still be proud of him. This is what he wanted, after all. So the letter finally proves that while Mikey was troubled and misguided in a lot of ways, he didn't abandon his brother into complete failure. He left just enough money to start building the dream they always had.
The second thing is that Carmy now knows for sure that his brother loved him; but more importantly, Mikey believed in Carmy more than he ever believed in himself. Those three simple words, "Let it rip," reveal one key thing to me - Mikey knew Carmy had a way better shot at making the restaurant work. Not just survive and hang on, but actually work.
But here's the thing, while Carmy has the raw talent and drive, he doesn't have the patience or people-skills to carry something like this though (this is why I think it matters that he retained a star as opposed to getting one from scratch. The difference is that to get a star, you have to build everything from the ground up, while to retain it, the foundation is already there). Which is where Sydney comes in.
While Carmy runs the Beef better than Mikey, they're still just surviving. Things only turn around when Sydney enters the picture. To summarise Season 1, Sydney has all the qualities Carmy is missing. Her raw talent isn't yet at the same level as him, but she's better at identifying her team's shortcomings and plugging any and all holes. She's also good at creating opportunity and fostering loyalty (such as when she sends Tina to culinary school, Marcus to Copenhagen, and hires Nat).
Sydney, in short, has the capability and will to transition everyone out of survival mode, and into full bear-mode. Carmy recognises this as early as Season 1. As soon as she's hired, Sydney asks for more responsibility from Carmy so she can fix the issues in the system they have. He agrees after tracking how well she does her job. Everyone eventually realises that yes, this place doesn't have to just survive. It can be good. But the pressure and new way of doing things eventually blows up since they all adjusted too quickly, and without addressing the core issues of why they were broken in the first place. This results in Carmy being trash to everyone and Sydney finally quitting.
One thing to note is that from the moment Sydney walks into the Beef, Carmy does everything in his power to give her everything she asks for. The only time he doesn't, is when money is involved and they can't afford whatever she's asking for. The only thing Carmy has to offer is his raw talent and his faith/trust in her. Other than that, he's a scrub and needs trauma counselling, and people are right to question what she's still doing with him. But then we get to Mikey's letter.
The other important aspect is that Sydney is gone when Richie gives him the letter. He has hit some kind of rock bottom, he even goes to a group meeting and starts trying to fix his life, albeit in small ways. He apologises to his team and by the time he earns the letter, he has come to terms with the the fact that his actions have consequences, and if he isn't careful, her will continue to lose thise he cares about. He finally does the one thing he couldn't do with Marcus and the rest of the team - he reaches out to Sydney. Right before he reads the letter, he texts her.
He still hasn't apologised to her and the first thing he says is "no acid." Sydney is rightfully confused, and maybe a little angry, at which point Carmy attempts an apology by saying, "my behaviour was not okay." That's clearly not good enough as an apology, but for Carmy, he may as well have written it in the skies. He wrongfully feels rejected by Syd in my opinion, mostly because he doesn't do the work of letting her know that he just got a message from Mikey. He wants her to comfort and reassure him, but she doesn't, because she doesn't know the full story. He hasn't let her in, and they have an emotionally incomplete exchange. He withdraws into himself again with the throwaway, "Yes, Chef. Last check is ready whenever." He finally puts away his phone and opens the letter. And the first words he sees are the exact same words he wanted to hear from Sydney: "I love you, dude. Let it rip."
This is probably me over-analysing, but one of the reasons I'm so sure the progression of events from the phone messages to the letter is significant, is because of not just the overall story framing, but how the text itself is presented to the audience. In the phone messages, Syd is on the left while Carmy is on the right side. In Mikey's letter, the part that says, "To Carmy" is on the left, while the part that says "from Mikey" is on the right side. In other words, thematically, Sydney is echoing Mikey by telling Carmy, "I love you, dude. Let it rip." We know Syd will say the last bit out loud when the Bear opens, and we also know that to Carmy, Syd is the Bear.
Additionally, this interaction emphasises various motifs specific to Syd and Carmy. In the same way that the show always emphasises Carmy giving Syd everything she wants, they tell us why that's always the case. Carmy knows Syd. Sometimes, even better than she knows herself. He's always able to anticipate her needs, wishes and wants because they have a bond that transcends friendship and (business) partnership. For example, not only does Carmy know that Syd is cooking when he's about to read the letter, he knows she probably hasn't added enough acid to whatever she's making (this is repeated in Season 2, Syd never adds enough acid and Carmy is always there to remind her). This, of course, culminates in the Season 4 finale when he tells her she's the Bear, but before we get to that, Carmy spends seasons 2 to 4 giving into Syd's wishes and creating a version of the Bear that SHE wants. This extends even further into the Mikey letter motif because the reason he's able to do all of this, is the cans of money they find, which is precisely when Sydney walks back into the Beef.
Two things are happening here: 1) this scene is a reversal of the first time Syd walked into the Beef (when Carmy didn't know her and what she is capable of); 2) the scene is this shows version of, "You had me at hello."
The first time Carmy and Syd meet, the restaurant is falling apart and money is bleeding from everywhere. But now, everyone is a little more healed and they are literally harvesting money out of tomato cans. Before, Carmy could only offer Syd his talent and trust, but now he's got the money to fund all the dreams she ever had. So when she walks in the second time, he doesn't even say hello, but instead jumps straight into telling her why she should stay: "Family style? Two tops, booths."
"Danish design, tasting menu at the bar," says Syd at the same time the background music sings, "Don't get sentimental."
"Window on the side--" says Carmy.
"For sandwiches," adds Syd, finishing his thought.
"Okay," nods Syd, a little shyly. "What do we call it?"
Here, Carmy doesn't say anything. He just continues to longingly look at Syd in a totally "platonic" way. We find out the name from the sign he puts on the front window, then transition into a family style lunch with everyone, then a memory of Carmy and Mikey making food together, and the season ends.
The framing seems intentional here, not just because of this scene alone, but because every single motive will be expanded on, and/or re-emphasised in a later season. For example, the first time I watched the show, I asked myself, but why does Syd come back? And the answer was very simple, for the same reason she came to the Beef in the first place - Carmy is still the best (meal) she's ever had. And while he is a traumatised sad boy who's broke, she knows that with him, she can reach her full potential. He proves this when he tells her to add acid to a dish he didn't even know she was making. He knows her flaws, but most importantly, he knows how to correct and soothe them away. He's her missing half. While she blindly hero-worshipped him before she met him, now she knows the man behind the genius. And yeah he's fucked up, but he sees her in a way that no one else ever has. She knows she can grow with him. She knows he'll do everything he can to make her dreams come true, so she chooses him. Again. She'll choose him yet again after attending Tiff's wedding and meeting even more of his family and being called "auntie" by Eva. Whenever there's a fork in the road, Syd has always chosen Carmy.
And what does Carmy do? He gives her the thing she's been asking for all along. Family style, two tops, booths and a tasting menu at the bar with a window for sandwiches. Translation: "I love you, dude." And in response, Carmy says, "I'll give you everything you want."
And he spends the next three seasons doing exactly that.
I'm sorry if this has been discussed before. I'm very new to tumblr and don't even know if I've done everything correctly. But I'm super obsessed with show (pretty sure it's my favourite of all time), and I don't have anyone to over-analyse with in the real life.