I absolutely agree with you, but 316 million is way beyond what banks are really capable of. Given the current low marketcap, there is a case in which a group of banks is accused of an attempt to launder more than the total crypto market capitalization! It sounds unbelievable, I know, but this is not some low quality news, the forbes wrote about it a while ago: https://www.forbes.com/sites/francescoppola/2018/09/30/the-banks-that-helped-danske-bank-estonia-launder-russian-money/. These people got caught, but how many more did everything successfully? Blockchain allows to view transactions and the community is very diversified with no key holders of bitcoin being around. Banks are watching others not to launder money but the problem is that nobody's watching banks and preventing such schemes.