You can thank Acorn for part of that.... they brought law suits and blockaded lenders that refused minorities mortgages that they couldn't afford. You can also thank the Libs for passing laws that required low income loans for housing to people that couldn't afford them, and then blocking any attempt to investigate and reform those stupid laws. You can also thank the Republicans for not having the guts to over ride all the above.
What has not been talked about much since this whole crisis, is lenders not caring about who they are lending to. To me, that is beyond reason to the point where I cannot even phathom it. But it did happen. People making less that $30,000 were allowed/encouraged to buy houses with values over $500,000. That's insane, and a huge cause of the housing crisis.