From a legal perspective there are no required internal controls on the flow of crypto going in and out. Apparently when there is a couple of hundred million worths of crypto sitting in a wallet, it becomes real tempting to go to the racetrack so to say.

Also, most of these exchanges have their own tokens which they control the supply of and keep as "assets" on their books. In doing so they can use these self printed tokens as collateral for loans. Add to that some nicely leveraged positions in all kinds of shitcoins and you start to understand how we got here.