Hedging is not the issue here. The problems you describe (toxic assets [which we, including Wall St., knew AFTER the fact by the way, not before- the subprime loans is another issue], overly high risk-taking, etc.) were the result of a underestimation of risk. Very few people, Wall St. or not, saw the bubble coming because everyone for the most part underestimated the systemic risk.But when hedging slides into burying toxic loans, thereby encouraging a free-for-all pursuit of maximum investment, regardless of risk, then there is no longer any buffer against recklessness, but rather an encouragement of it.
And if you think that Freddie and Fannie led the parade, you have it backwards. To now say that Freddie and Fannie over-investment was government leading the charge over the cliff is silly. They were incompentantly led for awhile, but they were following the crowd. Should they have acted more prudently? Of course, but to keep up with the money grabbers, they cannot now be blamed for leading the charge. That was the big bank, big investment houses.
It is not silly because they were a huge part of it. At the end of the day, this crisis was not solely the fault of Wall St., government, the Fed, or the home buyers- it was the fault of ALL of them.
And Fannie/Freddie played a large role in that. They became a market maker for a lot of the CDOs and MBSs, spending billions driven by a political goal dating back decades.
Bush made it his goal to encourage home investment at any risk. He thought that home ownership would lift the impoverished out of their hardship and stimulate the economy. If safeguards hadn't been removed by Clinton, the Republicans, and greed, he probably would have succeeded. Btw, Barney Frank wanted more rent assistance than home purchase assistance. The almost total collapse of our economy, and thereby most of the rest of the world, happened under emasculated government oversight, not because of 'government investment houses'.
This was not all Bush. Fannie and Freddie's growth and funding was largely the result of Democrat policies over the last few decades. Both parties were involved and both at fault. Part of this also goes beyond the political institutions and into the Fed, where Greenspan pushed a easy money policy.
In conclusion really it was a perfect storm. Everyone from the couple that wanted a house so bad they tried to pay for it on equity to the house flipper to the subprime lenders to Wall St. to the companies and governments who bought Wall St.'s products (Fannie/Freddie included) to the Fed that allowed leverage to the Federal government which incentivized risky behavior due to political dreams to regulatory bodies such as the SEC which didn't do their jobs are at fault. Without any one of those and a general understatement of risk that mostly everyone believed, it would not have been as bad as it was.