Let me save you time. Banks lobbied for it. The campaign used was that the US needed to 'modernize', or it risked letting the world take over the banking industry.
In fact, the bill with a lot of the deregulation was the 'financial services modernization act'. There were horror stories told of European markets becoming the world leaders.
What good Congressman can stand by and let 'obsolete' banking regulations from the 1930's hold back our great US industry? Time to modernize.
Only a small number of members spoke out against the bill, including a Senator who was the grandson of the member who had led the fight for Glass-Steagal, Byron Dorgan.
You can read a Bill Moyers piece on his speech and watch the video here:
http://billmoyers.com/content/a-senators-prophetic-words-then-and-now/
But a taste of it:
Now, the person who led the fight FOR that deregulation bill was Senator Phil Gramm, who Paul Krugman called 'the king of deregulation' and named as one of the two people most responsible for the 2008 crash (behind Alan Greenspan, whose Ayn Rand ultra deregulation ideology led him to terrible policy).
Remember 'Credit Default Swaps', the Wall Street creation that was a totally unregulated mechanism that was nothing but a tool for Wall Street to evade regulations on insurance, by providing 'insurance' with massive leverage and profits, which played a key role in the industry having a massive mess of owing itself trillions of dollars it couldn't begin to repay?
Legislation to prevent the government from regulating CDS's was co-sponsored by Phil Gramm, the - wait for it - "Commodities Futures Modernization Act of 2000".
By 2002 Gramm left the Senate having worked hard for the banks... immediately becoming an employee of bank UBS, lobbying for them. He was McCain's 2008 economics advisor.