The thing about Jack's Izzy is that he was never supposed to be Jack's Izzy. It was supposed to be a temporary thing, to teach Ed and Sam a lesson, to escape their constant tugging at him to decide who he was going with. He'd been beginning to feel more like their favourite toy, a pawn in their endless stupid fight, than a person whose opinion they actually cared about. He tells them he hasn't decided, that he doesn't want to decide, but it goes over their heads every time, too focused on "winning" him.
So when it comes to it, after Hornigold's gone, after they've won, and they're asking him again before he's even had chance to clean the blood from his sword, let alone his hands, he just blurts out "Jack"
To say everyone's shocked is an understatement. Sam and Ed's shocked "What's?" are only drowned out by Jack’s own. It's not like he hasn't known the whole time he was never in the running, he hadn't even asked Izzy because he knew he'd just laugh in his face. He loved Izzy just as much as they did, but it was never the same for Izzy. He never had the drive of Sam & Ed, the passion, the potential. He was Calico Jack, too stupid, too immature, too much of a drunk to be a worthy captain. (never mind that Izzy had always seen through that cover, seen the way he used the act to keep himself safe, seen that he was never really as drunk as he acted, seen the way he played people to get what he wanted. It didn't matter. He wasn't Ed or Sam, and that's all that really mattered in the end)
Izzy sits firm in his split second decision, telling them that he's fed up with all this bullshit, and Jack's the only one who listens to him, so he's going with him. Jack's not stupid enough to question Izzy further, so they take one of Hornigold's fleet & a handful of crew who hold no loyalty to the other boys, and set sail before it has a chance to turn into another mutiny.
The thing is, Izzy never really intended to stay. His plan was to leave with Jack for a month or so, fucking around achieving nothing while his boys got their heads out of their asses, then go back once hes actually had space to make a decision, to decide who he wants to be, free of anyone else's expectations. Only, having Izzy there to impress makes Jack pull his act together fast. He's desperate to prove he's worthy of Izzy's time, cutting back on all the dicking around and making a genuine effort to be a worthy Captain for him. He's not perfect by any means, but they're actually doing ok.
And for Izzy, it's like someone's lifted a weight off of his shoulders. He hadn't realised it until he was away, but being with Sam & Ed had felt crushing towards the end, both of them expecting so much from him, wanting him to be someone who wasn't quite him, wanting him to help them build a legend. And maybe he wanted that, maybe he would love it in another life, but it's also nice to not have expectations. Jack never wants him to be anything other than himself, and it's been pretty nice, learning who Izzy Hands is. He thinks he might like the guy.
So it goes from there. A month passes and Izzy makes no mention of meeting up with the others. Then two, then three, and before long he's forgetting that he ever seriously planned to leave. He stays, and they make it work, together. It's not perfect, it was never going to be, but they have something that makes them both happy. And that's enough.
