In addition to what's said below, if the prosecutors are being driven by federal/national-level concerns, then the goal is probably less about punishing a bank'

In addition to what's said below, if the prosecutors are being driven by federal/national-level concerns, then the goal is probably less about punishing a bank's officers, and more about getting more information on hostile nation states, and possibly financially neutering them. That's powerful, and far further up the chain of national interests. Apart from that, my sincere apologies for arguing even slightly against against jail time for the banksters.