How did banks contribute to the crisis of 2008-2009?

Banks contributed to the 2008-2009 financial crisis by engaging in risky lending practices, particularly in the subprime mortgage market, where they issued loans to borrowers with poor credit histories. They also securitized these high-risk mortgages, bundling them into complex financial products that were sold to investors, which obscured the true level of risk. Additionally, banks underestimated the potential for widespread defaults and leveraged their investments heavily, exacerbating the crisis when housing prices fell and defaults surged. This combination of risk-taking and inadequate regulation led to significant losses and a loss of confidence in the financial system.