That doesn't seem to be the case, at least in a lot of the major recent crises like mortgage refinancing. It wasn't that they were running the numbers better; it was that they were misrepresenting the underlying quality of the securities in question. Look at the MBIA lawsuit where it was clear that folks on the selling side knew that the securities were garbage. Same with Enron.

There's a popular saying on Wall Street: YBGIBG. It means "you'll be gone, I'll be gone"... by the time the scam gets exposed, the folks who perpetuated will have received their bonuses and be long gone.