It essentially gets moved around banks, at each stage the account owner is taking a cut but ultimately it requires a friendly bank to hold the majority of the funds and not give it back when requested, usually because you have set up some kind of plausible route for the funds to be in your possession.

https://en.m.wikipedia.org/wiki/Bangladesh_Bank_heist

$81m was sent to a bank in the Philippines and less than 25% was recovered. Other banks had success is recovering all the funds sent through them as part of the same heist.