Though many politicians may point to the idea that low interest rates are helping the big banks perform well through lowered borrowing costs, and that the stock price performance of some of these "too big to fail" banks is also partly due to investor confidence that these banks would have the tacit support of the government should they need it, in this video, Fool analyst David Hanson tells investors the real reason these big banks are shooting upward today. To understand what's been lifting these banks into the stratosphere now, you only need to look back at where they were at the end of 2011.