Republican controlled congress voted to remove restrictions that were in place since the crash in 1929 from banks and investment companies.
Phil Graham (R-Tex) authored the bill that was passed by the Republican controlled Congress. And, here is an interesting side note: weeks after the bill passed, Grahams wife became a board member of one of the largest banks in the world.
Republicans bought into Reagan-era free market ideology and deregulated the banks and the financial industry, virtually guaranteeing that we would have a repeat of 1929, when lack of regulation allowed abuses that led to the great stock market crash.