I think you are getting to the core of the issue, which is that when the underwriter is decoupled from the result, they must either be regulated or their customers (the real creditors) must have skin in the game. The regulations have been ineffective (so far), and the creditors have always been bailed out; we should not be surprised that creditors are unscrupulous about lending to questionable borrowers.

Or you know we could enforce our laws. Many of those loans were fraudulent and outright criminal to grant. The threat of years in jail is a pretty good way to keep people honest.