The Glass-Steagall Act, passed in 1933, mandated the separation of commercial and investment banking in order to protect depositors from the hazards of risky investment and speculation.
For fifty plus years, the legislation did what its sponsors wanted it to do, which was to prevent a second major economic recession with consequences that only benefit the wealthy.
Loopholes in Section 20 were put in place starting in 1986 through 1997 that effectively renders the act obsolete.
Repealing it put a greater burden on the banks and the taxpayer is at greater risk through the FDIC and other insurance programs of the government.