Losses on U.S. residential mortgage loans are too small to explain the magnitude of the 2008 financial crisis. Total losses, including both losses realized to date and those yet to be realized, should fall in the range of $750 billion to $2 trillion. The global magnitude of the crisis is significantly larger, probably in the range of $5 trillion to $15 trillion, depending on the measuring approach. This implies that losses on residential mortgage loans cannot be the main cause of the crisis. They can only be a trigger that unleashed the true causes. The failure (or near failure) of a significant number of major financial firms suggests that high leverage and strong risk appetites were important immediate causes of the crisis. However, explaining the sources of high leverage and strong risk appetites requires probing for deeper causes that developed over a longer period. This article proposes deeper causes that include securities firms' conversion from partnerships to corporations, the 30-year deregulation trend, the quant movement, the spread of risk-taking culture throughout the financial industry, and globalization.