That's why it was such a disaster--the banks knew that many of the later mortgages were made to people with dodgy credit histories. So, they packaged them up and securitized them, getting them off their books. Wall Street (think Merrill Lynch, Lehman, Bear Stearns, AIG) wound up holding the bag, as well as foreign entities in Germany and Iceland. And, if a creditor was aggressive in trying to collect on those loans, it was labelled a predatory lender.
That is not to excuse the inept and greedy collection practices of Wells Fargo and Bank America, BTW. But, that was after the fact corruption, not before the fact causation.
If at first you don’t succeed, search for the votes and try again.
Fannie May and Freddie Mac. Chris Dodd and Barney Frank come to mind.