Michael Lewis has a great story in Portfolio looking at the demise of Wall Street.
He tells the story of Steve Eisman, a hedge-fund manager who was a long-time cynic about Wall Street and who won big by betting against subprime mortgages and CDOs.

Lewis writes about the ignorance and crookedness that caused the mess.

The funny thing, looking back on it, is how long it took for even someone who predicted the disaster to grasp its root causes. They were learning about this on the fly, shorting the bonds and then trying to figure out what they had done. Eisman knew subprime lenders could be scumbags. What he underestimated was the total unabashed complicity of the upper class of American capitalism. For instance, he knew that the big Wall Street investment banks took huge piles of loans that in and of themselves might be rated BBB, threw them into a trust, carved the trust into tranches, and wound up with 60 percent of the new total being rated AAA.

But he couldn’t figure out exactly how the rating agencies justified turning BBB loans into AAA-rated bonds. “I didn’t understand how they were turning all this garbage into gold,” he says. He brought some of the bond people from Goldman Sachs, Lehman Brothers, and UBS over for a visit. “We always asked the same question,” says Eisman. “Where are the rating agencies in all of this? And I’d always get the same reaction. It was a smirk.” He called Standard & Poor’s and asked what would happen to default rates if real estate prices fell. The man at S&P couldn’t say; its model for home prices had no ability to accept a negative number. “They were just assuming home prices would keep going up,” Eisman says.

And he comes back around and illustrates how Wall Street going public led to the scandal by allowing its partners to offload risk onto shareholders.

No investment bank owned by its employees would have levered itself 35 to 1 or bought and held $50 billion in mezzanine C.D.O.’s. I doubt any partnership would have sought to game the rating agencies or leap into bed with loan sharks or even allow mezzanine C.D.O.’s to be sold to its customers. The hoped-for short-term gain would not have justified the long-term hit.

It’s a long story and worth reading every word.

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Ryan Chittum is a former Wall Street Journal reporter, and deputy editor of The Audit, CJR's business section. If you see notable business journalism, give him a heads-up at rc2538@columbia.edu. Follow him on Twitter at @ryanchittum.