re: History
The current collapse was caused by a mortgage industry that believed it was insulated by political power and Federal funding from the consequences of stupid actions. Basically, the same thing that happened with the savings and loan crisis.
You can look up for yourself which entities did this insulating, who was running them, and where the money was flowing between these entities and the private sector. For extra credit, look up what the people in charge back then are in charge of now.