The way I understand this whole "Chain of Blame" is this:
Clinton encouraged banks to give subprime loans to poor people to enable them to acquire housing and stimulate that part of the market.
In 1999, lobbyists successfully removed a Great Depression era act (S?????-G????? Act) that enabled to give sub-prime mortgages to anyone without restrictions or checks.
Mortgage backed securities allowed banks to transfer the risk to other institutions entirely. By bundling good mortgages with stinkers, they got great ratings on the bundles, and were able to sell them easily. The elimination of risk/retribution further spurred banks to make loans to anyone for any amount. Some customers willingly took advantage of this, some of them used this to take out loans they thought they genuinely qualified for.
Big investment banks and financial institutions bought into the securities, seeing them as highly rewarding, low risk investments with sterling ratings.
Personally, I see the banks that churned out these mortgages as mostly responsible, then the legislators that removed all limits, then followed by credit ratings/big financial institutions for not checking up on what these things were, finally, by consumers that took advantage of the situation.
