1) SDNY was surely watching Rudy closely enough to know he was headed to Ukraine, just like they knew Lev and Igor we’re leaving. They let Rudy go because they know he’ll further incriminate himself over there. It’ll make for a more comprehensive criminal case against him.
2) Yes, Rudy will come back home. He’s convinced himself he’s somehow innocent, and that he’s too beloved to ever be convicted, so he can therefore beat the rap. So why would he flee? As opposed to Lev and Igor, two pawns who knew they were screwed, and therefore tried to flee.
3) The case against Rudy is already very strong, based on publicly available evidence alone. But they’re probably trying to make it so overwhelming, Trump will be afraid to try to pardon him, for fear of the fallout. Might as well wait to arrest Rudy until the case is complete.
4) Mueller botched a lot, but one thing he nailed was letting Manafort out on house arrest. Manafort promptly got caught witness tampering. Made the case against him so much uglier. Made it harder for Trump to pardon him. Ensured that Manafort got a longer prison sentence.
5) Other than the catharsis of us getting to see Rudy in handcuffs sooner, I can’t think of a single reason for the SDNY to have arrested him before he could go to Ukraine. And there are several smart reasons not to have him arrested yet. That’s not popular, but it’s just reality
