That's the topic of as Glass-Steagall's Demise Inevitable and Unimportant? by law prof Arthur Wilmarth. Here's the abstract:
The demise of the Glass-Steagall Act was the result of affirmative policy decisions by federal regulators and Congress, and it was not the inevitable byproduct of market forces. Economic disruptions and financial innovations posed serious challenges to the viability of Glass-Steagall, beginning in the 1970s. However, federal regulators and Congress could have defended Glass-Steagall and made necessary adjustments to preserve its effectiveness. Instead, they supported efforts by large financial institutions to break down Glass-Steagall’s structural barriers, which separated commercial banks from securities firms and insurance companies.
Federal agencies opened a number of loopholes in Glass-Steagall’s barriers during the 1980s and 1990s. However, those loopholes were subject to many restrictions and did not allow banks to establish full-scale affiliations with securities firms and insurance companies. The largest banks needed two major pieces of legislation to achieve their longstanding goal of becoming full-service universal banks. First, big banks and their trade associations persuaded Congress to pass the Gramm-Leach-Bliley Act of 1999 (GLBA). GLBA authorized the creation of financial holding companies that could own banking, securities, and insurance subsidiaries. Second, the financial industry convinced Congress to adopt the Commodity Futures Modernization Act of 2000 (CFMA). CFMA insulated over-the-counter (OTC) derivatives from substantive regulation under both federal and state laws.
The campaigns that led to the enactment of GLBA and CFMA lasted two decades and cost hundreds of millions of dollars. The largest financial institutions and their trade associations would not have pursued those campaigns unless they believed that both statutes would have great importance.
GLBA and CFMA proved to be highly consequential laws. They enabled banking organizations to become much larger and more complex and to offer a far broader range of financial products. They transformed the U.S. financial system from a decentralized system of independent financial sectors into a highly consolidated industry dominated by a small group of giant financial conglomerates. GLBA and CFMA promoted explosive growth in shadow banking, securitization, and OTC derivatives between 2000 and 2007. All three of those markets played key roles in fueling the toxic credit boom and unstable financial conditions that led to the financial crisis of 2007-09.
