If money wasn't needed. If people had access to dignified work to pay for housing, food and health, they would have a choice.
Cop work is always available, on a very low entry bar, paying generally better than equivalent positions elsewhere. And shitty people get to vent their violence unchecked.
Nice cops "just" have to sell their should a bit. Some people get desperate and are willing to pay the consciousness price.
In my opinion these positions shouldn't even be available, the whole chain of command should be replaced by people representing the oppressed classes, committed to ending oppression.
I'm not defending police, I just think the criticism has to focus on the institution problem, not at the individual problem. Individuals are insignificant in the grand scheme of things, systems are everything.