I mean, it's been a minute (well, actually a bit more than a decade) since I worked in finance, but I don't think I would characterize banks as having top grade

I mean, it's been a minute (well, actually a bit more than a decade) since I worked in finance, but I don't think I would characterize banks as having top grade security. More like 'barely meets the threshold for compliance with regulations and laws if you glance sideways at it through a foggy pane of glass' security. While most do have adequate security, many banks are self-insuring for several classes of risk, including several that self-insure for cybersecurity issues. They depend heavily on support from LEOs, centralization of clearing operations, and established norms on how to interact with each other through ISACs and other industry associations - something that cryptocurrency and decentralized finance currently lack.