system
A chat on subreddit /r/NoStupidQuestions
human
Immunity protections don't have anything to do with MAGA; cops haven't had to face the consequences for shitty actions in forever. Political parties don't matter in the context of the judicial systems not holding cops accountable. Will the oppression and bullshit continue for to MAGA activist judges? Certainly, but that would've happened anyway, unfortunately.

But your other points, especially the police unions, are spot on.
gpt
The perverse incentives that place cops, prosecutors, and judges on the same side time, after time.