The need for the buyouts is primarily driven by two giant factors:
1> Deregulation of financial institutions which led to irresponsible loans. The biggest advocates for deregulation? Alan Greenspan and people like Senator Phil Gramm, John McCain's chief economic advisor. Republicans are traditionally the champions of deregulation of financial institutions, and many still view it as the solution to what we are facing, and not a cause of the problem.
2> The collapse of the housing bubble, which was driven in large part by wealthy real estate speculators, who were arguably the prime beneficiaries of the Bush administration tax cuts, which were disproportionately for the rich. Rather than focusing tax cuts towards the low and middle class in order to increase spending and counteract an economic slowdown early in the Bush administration, the Bush tax cuts were focused on the wealthy, giving them more money to save and invest.
... and so, real estate prices skyrocketed for everyone, based largely on increased speculation, while at the same time, loans were less secured than ever, and many who ordinarily wouldn't be able to buy houses were courted by predatory lenders, offering adjustable rate mortgages. People came to believe that investing in real estate was sure money, which, from their perspective, made "zero money down" loans and adjustable rate mortgages appear like "free money"... which, of course, it wasn't.
There is, of course, another big reason why deregulation came about. It happened because of the increased, damaging influence of lobbyists and big money contributions to politicians. The financial industry wanted deregulation, because they saw the potential for making more money. They bought and got their deregulation, and now... everyone who *WAS* responsible with their money loses, as their tax dollars go to pay for other people's mistakes.
Apparently, Republican Party socialism is okay, so long as it is used to avert crisises largely of their own making. But Democratic Party socialism, which tries to preemptively address crisises... now *THAT'S* unamerican!