Work in police exposes people to many traumatic situations. You may encounter very tragic situations or cases where your efforts to help result in more damages. Facing a gun is traumatic. This work can hurt even the strongest and can ruin their life. I have more difficulties to imagine these people selling their soul just for money. Often it is easier to leave police for better paid private activities.
> 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
IMHO, corruption in french police is not widespread. The situation of police in Marseille (your link) is very extreme and not really representative of the whole country. The optimistic view is that police is fighting very hard to stop corruption and even in terrible places like Marseille, they have succeded to stop a big case.