It is true that there were a lot of enabling actors dating back to the 1970;s, and not just in the financial side of the house. The apathy of the government on immigration enforcement was also a component.
All of those actions - Clinton, Carter, Barney Frank, immigration amnesties and lack of enforcement, Bush/Rove/McCain open borders attempts - were just setting up the conditions for what has happened.
It was not until the illegal flood occurred that the subsequent bad activities could take place. All of the previous setups were waiting for some event/market to take advantage of it. Illegal aliens were the seed that became available to plant in these fertile but unused fields.
The derivative paper schemes, the easy loans, the excess money supply, all came together when the illegal Hispanic house hunters showed up.
And they all cleaned up, moved on, and left us with the cleanup. The final irony is that we the taxpayers are going to be asked to pay to keep these illegals in their foreclosed homes.
The "affordable housing" policy and sub-prime mortgages were originally designed to benefit blacks. The Congressional Black Caucus was the driving force behind the policy. And, indeed, blacks were the primary beneficiaries of the the program well before the illegals became a market.
Toward the end, whites also became beneficiaries, as well, when many discovered they could "afford" more house than they'd planned.
It was Freddie Mac and Fannie Mae's policies that drove the housing bubble -- the result of a political policy that distorted the market and corrupted everybody associated with it.
Illegals are a separate issue. They were among those benefitting, to be sure. But the corruption was well underway without them.