It might have been more complicated than that. Remember, when he took office President Obama faced a financial system swirling around the drain. He had to work with major US banks, the Federal Reserve, and foreign banks and central banks to rescue the economy. Perhaps these delicate negotiations and arrangements left little in the way of wiggle room for him. He might have been boxed in.
This might also explain his less-than aggressive stance with regard to prosecuting bankers; he was focused on saving the financial system as part of a wider effort of rescuing the economy. And our economic picture was looking really dark in 2008/2009.