The New York Times quotes William Black, a law professor and director of litigation during the late 1980s savings and loan crisis:
“This is not some evil conspiracy of two guys sitting in a room saying we should let people create crony capitalism and steal with impunity. But their policies have created an exceptional criminogenic environment. There were no criminal referrals from the regulators. No fraud working groups. No national task force. There has been no effective punishment of the elites here.”
In other words, despite that first line, two guys (Tim Geithner at the time President of the NY Fed and Andrew Cuomo at the time NY Attorney General) sitting in a room decided that Wall Street Elites could steal with impunity. The only thing wrong with this very general account is that more than two guys were involved.
It's clear that there was and is rampant fraud. Why hasn't anyone been prosecuted? Because the people deciding on whether there will be prosecutions are themselves part of the fraud. It's absurd, after all, to prosecute yourself.