From Wikipedia:
[Quote]
During May 2010, Warren Buffett and Paul Volcker separately described questionable assumptions or judgments underlying the U.S. financial and economic system that contributed to the crisis. These assumptions included: 1) Housing prices would not fall dramatically;[52] 2) Free and open financial markets supported by sophisticated financial engineering would most effectively support market efficiency and stability, directing funds to the most profitable and productive uses; 3) Concepts embedded in mathematics and physics could be directly adapted to markets, in the form of various financial models used to evaluate credit risk; 4) Economic imbalances, such as large trade deficits and low savings rates indicative of over-consumption, were sustainable; and 5) Stronger regulation of the shadow banking system and derivatives markets was not needed.[53]
The U.S. Financial Crisis Inquiry Commission reported its findings in January 2011. It concluded that "the crisis was avoidable and was caused by: Widespread failures in financial regulation, including the Federal Reserve’s failure to stem the tide of toxic mortgages; Dramatic breakdowns in corporate governance including too many financial firms acting recklessly and taking on too much risk; An explosive mix of excessive borrowing and risk by households and Wall Street that put the financial system on a collision course with crisis; Key policy makers ill prepared for the crisis, lacking a full understanding of the financial system they oversaw; and systemic breaches in accountability and ethics at all levels.“[54]
https://en.wikipedia.org/wiki/Subprime_mortgage_crisis
And another:
The Financial Crisis Inquiry Commission reported in January 2011 that "the CRA was not a significant factor in subprime lending or the crisis. Many subprime lenders were not subject to the CRA. Research indicates only 6% of high-cost loans – a proxy for subprime loans – had any connection to the law. Loans made by CRA-regulated lenders in the neighborhoods in which they were required to lend were half as likely to default as similar loans made in the same neighborhoods by independent mortgage originators not subject to the law."[67] Critics claim that the use of the high-interest-rate proxy distorts results because government programs generally promote low-interest rate loans – even when the loans are to borrowers who are clearly subprime.[152] Several economist maintain that Community Reinvestment Act loans outperformed other "subprime" mortgages, and GSE mortgages performed better than private label securitizations.[2][27]
Good lord, I haven't read this wikipedia article before, but jesus christ, there were many causes, fannie mae and freddie mac, being the least responsible for the causes.