There are no national standards, so every city, county, and state get to determine the requirements for being a police officer. There's typically no educational

There are no national standards, so every city, county, and state get to determine the requirements for being a police officer. There's typically no educational requirement beyond high school. The prospect of being able to legally bully people obviously attracts some amount of people of a certain mindset. So if you don't try to filter for that, you get this situation. There's several other factors, like our concept of "qualified immunity", "thin blue line" attitudes, and powerful police unions that contribute to the environment where you can do whatever you want with impunity.