What led to the failure of a large number of banks in the 1930's

The companies were manufacturing more than they could sell; same goes for the food producers. This meant that the people couldn't earn money and investors couldn't get their money back. When the stock market crashed, people lost millions and millions of dollars on a nationwide scale. This meant there was no money and banks couldn't work properly and had to start closing down. They couldn't give loans because people couldn't repay them, and this meant no interests.