The big culprit in the housing bust was too many people with little or no personal money in their investment. (Had a lab Mgr that bought a 3rd house with no money down as an investment. She walked away from the house when the market started to tank with no financial repercussions.) The big losers were the lower end buyers that used their savings and got crushed. It is happening again. Fannie and Freddie are now buying 3% down mortgages and looking to lower it to zero%.
Oh goody, the Govt is here to help us! Again.