Via DeLong:
Matthew Yglesias's Theory of the Obama Administration in 2010: Excessive Reliance on the Second Derivative.
Long story short: the Obama administration saw that it's intervention had stopped the employment free-fall of and concluded that it would just turn itself around. Wrong. That was the point at which more help was needed to reverse the damage. I would add that the Obama administration also under-estimated the extent of the damage that was already done when they came into office.