Most banks, not just on Wall Street, are only after one thing: money. They will do whatever it takes to get more and more money. This is exactly the behavior that causes corruption. People get greedy and cannot stop themselves, and have no limit on what they will do to get more.
Most Wall Street banks are not corrupt. Although the industry has received bad press, many of those that work at the bank are hard working, ethical people. If these banks were corrupt, nobody would do business with them. However, there is an element of greed that causes some individuals to cross the line.
No, most Wall Street banks are not corrupt. People only hear about the Wall Street banks that are corrupt because these are the only banks that need to make the news. The banks that do nothing wrong are not talked about. This does not mean that Wall Street banks are corrupt.
Most Wall Street banks are not corrupt. This is simply a political narrative to advance blamer for whenever something goes wrong on wall street. Banks, like any other business are not infallible. To lump all banks together as bad is not only intellectually lazy, it is disingenuous by any measure.