Looks like human species is not so smart as they think.
Repeated mistakes and nothing learned.
Lack of education. It's everywhere around us right now, popping up to the surface like oil in water. If someone considers holding money in a bank or holding their gold in a bank safe is secure, they'll have 0 concerns about holding their money on an online exchange. The saddest thing about it is that a bank can close/legally steal their funds just as easy as the online exchanges do. Nothing sits safer in any pocket other than yours. It just happens so that banks don't do this very often. But when it happens, it's wild.