> I have more difficulties to imagine these people selling their soul just for money.

Despite what you seem to think, police are not more righteous or just than any other person, as we've seen through the constant abuse, corruption, and violence perpetrated by LEO and intelligence agencies. In fact, due to the kind of people drawn to the positions and the screening to filter out people who are too intelligent to blindly follow the state, I would argue that "these people are in fact MORE likely to fall for corruption or "sell their soul just for money" as you say