What if this is just me now?

But the Karen and Frank chemistry was an accident. They caught lightning in a bottle between two characters who never even interact in the comics, but the actors just go crazy in a room with each other.

And they assumed that the Punisher's audience skewed heavily male, that they'd refuse to watch anything not already established in the comics, and that they'd scorn any new plot where The Punisher feels love for anyone, so the writers/producers never fully went there. Even though they clearly know that Frank is made all the more interesting, all the more tragic, when he's not just wallowing in grief for a lost family- he's actively denying the potential of healing and love with a new person. He's consistently being offered a redemptive escape from the violent path he's chosen and he consistently denies it, even though it's clear as day how badly he wants it. That's a more interesting choice! It makes him more pathetic and self-denying, it shows him thinking that he doesn't deserve healing, it shows his conflicted awareness of his own morality, it makes him worse, it makes it clear that this character is tragic instead of aspirational.

So they gave as many hints as they could. The near kiss in the elevator, Karen's heartbeat, the dress Maria wears in his last vision of her (as he lets go of her hand) matching the fabric of the blouse Karen wore the first time he ever saw her, Karen insisting he try to love someone else instead of another war, Micro saying "that's my family that's my wife" and Frank responding "so is Karen." They made it as obvious as they could without actually saying it because they didn't want to piss off the fan base who wants Frank to be a static, stoic, one dimensional vengeance machine.

But now they're back after SEVEN YEARS and they're not fucking around. The first time they're on screen together it is Textually Acknowledged and Stated Out Loud that Frank Castle's heart does the fucking samba when he looks at Karen Page. Matt, the Human Polygraph Test, tells Karen that Frank loves her and that he knows how she feels about him too. (Not to even mention the way he looks at her and acts around her, because Jesus Christ, I have never seen anyone more obviously lovesick.)