The unions are highly invested in police bad behavior. They are the real controlling force behind the police departments. They have even more power than the Chief, because they pick the Chief, and they hold a tremendous amount of political clout as well, they pick politicians.
It’s good that they are in the spotlight now, because at least people can see where the corruption initiates; and that’s important. Because as long as police unions remain unchanged, bad cops will always be preferred over good cops. And the corruption will spread to an unbearable point, where you have police killing people gleefully, because as you pointed out, there isn’t appropriate oversight.
As it stands, police union oversight rewards bad behavior, and encourages violent, vicious psychopathically murderous behavior. Even worse, they truly do not see anything wrong with this. They have the ability to justify it, and have done so, repeatedly; and this is why so little has changed. It is a profession that was established in inhumanity (slave-catching) and it never fully abandoned those roots.
I’m sorry you’re shocked, but I’d you knew the history and inner-workings of these systems, you would not be. You’d understand, it’s par for the course.