Because, all this while, the Republicans controlled Congress.
The Democrats were able to block reform only so long as several Republican Senators and Congressmen went along with them.
And, if the cries for reform were so strong, why didn't the GOP majority ever make Fannie and Freddie the major issue they should've been?
Fact is, the GOP majority didn't have the courage to follow-through on their efforts at reform. The time for them to be "screaming from the rooftops" was in 2005. Not now.
Through their inaction, the Republicans were almost as complicit in the meltdown as Democrats.
Simple. We were in the middle of two wars. The Republican administration had to buy off the Democrats in order to fund the wars. The Democrats held the country hostage for their own political gain.