Why are there so many corrupt cops?

There actually aren't so many, but media coverage makes it seem that way. Statistically, the amount of unjustified shootings by police in the United States are very low. Public opinion has been shaped, and even when the officer has been investigated and cleared, they are held guilty by untrusting civilians. However, if you look at the other side of it, there were 70 US officers shot and killed in the line of duty just in the first 7 months of 2016.