There is plenty of blame to go around, but the most important bank deregulation was the repeal of the Glass-Stegall act that had been in place since FDR's bank reforms during the Great Repression. Glass Stegall was repealed on Clinton's watch.
Glass-Steagall “repeal” and the financial crisis
Robert Kuttner, Joseph Stiglitz, Elizabeth Warren, Robert Weissman, and others have tied Glass-Steagall repeal to the late-2000s financial crisis. Kuttner acknowledged “de facto enroads” before Glass-Steagall “repeal” but argued the GLBA’s “repeal” had permitted “super-banks” to “re-enact the same kinds of structural conflicts of interest that were endemic in the 1920s”, which he characterized as “lending to speculators, packaging and securitizing credits and then selling them off, wholesale or retail, and extracting fees at every step along the way.” Stiglitz argued “the most important consequence of Glass-Steagall repeal” was in changing the culture of commercial banking so that the “bigger risk” culture of investment banking “came out on top.” He also argued the GLBA “created ever larger banks that were too big to be allowed to fail”, which “provided incentives for excessive risk taking.” Warren explained Glass-Steagall had kept banks from doing “crazy things.” She credited FDIC insurance, the Glass-Steagall separation of investment banking, and SEC regulations as providing “50 years without a crisis” and argued that crises returned in the 1980s with the “pulling away of the threads” of regulation. Weissman agrees with Stiglitz that the “most important effect” of Glass-Steagall “repeal” was to “change the culture of commercial banking to emulate Wall Street's high-risk speculative betting approach.”