Glass-Steagall had nothing -- NOTHING -- to do with the 2008 meltdown. Anybody who said that it did was selling you swampland in Florida, probably to cover their own culpability in the mess.
If you doubt me, then please explain how the repeal of Glass-Steagall:
(a) ...created or accelerated the bubble in housing prices; or
(b) ...caused the collapse of that bubble; or
(c) ...led to the events in which the revaluing of mortgage-backed securities caused the financial giants to go out of business.
You will find that the ability to allow a single holding company to own an investment bank and a commercial bank at the same time affected none of those things.