It’s too bad that Peter Wallison’s exceptionally clear and concise explanation of the causes of the housing bubble  is available in full only to subscribers to the Wall Street Journal. Here’s his conclusion:
The narrative that came out of these events [the government-sponsored bubble and its inevitable bursting] —largely propagated by government officials and accepted by a credulous media—was that the private sector’s greed and risk-taking caused the financial crisis and the government’s policies were not responsible. This narrative stimulated the punitive Dodd-Frank Act—fittingly named after Congress’s two key supporters of the government’s destructive housing policies. It also gave us the occupiers of Wall Street.