I think it's a mistake to assume anything connected to FTX or that SBF did is by default shady or criminal in nature. Like, if you found out they purchased their company toilet paper from Amazon - would that indicate some nefarious motivations?
Yes, they're criminals who belong in jail but only for the way they managed their balance sheet. They were also great builders who had awesome products and wanted to do all the great things they said they wanted to do.
Buying a bank is something probably every crypto exchange has considered doing, so they can have access to the financial system and not have to pay massive amounts of money and have huge headaches processing payments for their customers. I'm surprised Coinbase doesn't own one by now - or perhaps they do.