The short answers.
Incest. The people charged with solving the problems were the same people who caused it.
Linkage. The 6 largest banks controlled most of the country's GDP. It was uncharted territory, and holding it together was the main concern.
Mismanagement. Obama's directions weren't always followed and he didn't follow up on that.
Fear. Obama was pre-occupied by his health care plan, didn't want to "cross" wealthy interests.
Overall, I think he should be impeached and convicted for not prosecuting these people. And to not prosecute Bush, Cheney, Powell, Rice, et al.