I had a cocktail conversation a few years ago with a lady who worked for Accredited Lending (LEND), and her job was to provide documents that justified the lies made by the real estate agents and borrowers long enough they could repackage the loans and sell them to Countrywide so that Countrywide could repackage them and sold them to Fannie Mae.
She said that both buyers and agents would sign and do anything to get the home sale done (buyers are stupid and agents need their commission) and she said that making the loans look presentable was a challenge. She mentioned a procedure that was called “Cut and Paste” but didn’t go into much detail. I mentioned that her job sounded a lot like loan fraud and the conversation sort of ended.
My own personal belief, based on very little evidence, is that fraud was very widespread and at every level of the foodchain.