Hard to say but banks like JP Morgan underwrote the structured products and kept the equity piece on their books. They then insured that piece with AIG, which allowed them to underwrite even more crappy structured products to keep them on their books.
That's great and all, but Glass Steagall wasn't designed to prevent that.
There were certainly MBS under GS.
Yes, but bank equity was higher, the quality of the MBS was higher and there was less MBS generally.