What was the main cause for the downfall of the U.S. economy?

Greed and Capitalism are easy to blame but the real reason why things like the housing bubble busted and the mortgage crisis is as a result of years of politicians and non profits such as ACORN forcing firms to lend to people they wouldn't normally lend to. Sometimes through legislation or through the fed's ability to flood the market with cheap credit. This money all went into the housing market creating the crisis we see today.