The low level guys were just doing their jobs, and each individual transaction was mostly legal. A few weren't but it's hard to sort out which ones. Maybe the management should be responsible for ensuring that nobody ever did anything illegal, but they can't really supervise everything all the time, can they?
Poof. Guilt is just a rounding error that all rounds down to zero. The government passes some new regulations to prevent that particular scenario from happening again, and the same people set about finding a new scam.
Once you get to the top, the act of pulling up the ladders behind you is "just" self preservation.
there's a separate certification function for managing certification function employees, and they're jointly liable for anything they do