You can never ever prove Glass-Steagall would have prevented the crisis, never. You can only look at the factors that created the crisis.
Banks were forced to grant mortgages to the non credit worthy because of the community reinvestment act. That's what started this ball rolling back in 1992. Not because of the repeal of Glass-Steagall in 1999.
Stop conjuring up this red herring, it does not exist.
Yes, I can. There was more to the 'crisis' than just the big banks' potiential to fail. Here is a list of bank failures since 2008:
Banks fail every year, but there was an excess of this happening during the recession because these banks were able to do things that weren't legal in Glass Steagall.