Those engaged in evil always go after those exposing their villainy the most viciously.
Good cops quit, good cops go to jail. All good cops are former cops.
So many people go into fields knowing there is glaring flaws and issues but have some sense they’ll somehow be able to change things from within, for the better and time and time again does this fail. Just the structure and culture of things like this are so ingrained into the field, hardly anything will budge. Plus even if you altered the culture in one department it’s a drop in the bucket compared to how much power police unions have. These things need to be dismantled completely for any meaningful change to exist.