Extradition treaty mainly just lets some foreign country start a process in local courts to hand someone over.
You need to butter up a place with adversarial relations.
Or go somewhere with ironclad constitutional protections against extradition. And even then, e.g. France only has those for its own citizens and may still prosecute you locally for your crimes abroad.
Its a big world out there and a shockingly large portion is free of recognized government control. In such places you pretty much live by your own bootstraps rather than what some far away western country says, at least on the individual level.
What really really shocks me though is that SBF didn't just jump on a yacht out right after the failure as he easily could have done. If he had sailed to the right part of Latam or West Africa he'd have a decent chance at not getting caught.