^ Read the book "Greedy Bastards" by Dylan Ratigan. He breaks it down to a very simple explanation to where basically the banks lobbied to Congress to let them insure their own mortgage loans, which removed all incentive of them caring if the mortgage was paid, b.c they would collect no matter what.

And then began the sub-prime mortgage rates that caused that particular bubble.

Oh yeah, and then they got bailed out on top of it.