why are corrupt public officials corrupt?

An anonymous poster posed the question:

Is this the reason why the "bad guys" go into politics... to enrich themselves?

Here's my three part answer to why public officials are corrupt:

1. Some unethical people and sociopaths are attracted to politics.
2. The system creates pressure to behave in a corrupt way.
3. People who are willing to abuse power have an advantage in politics.

The solution to corruption is always the same.

a. Increase transparency
b. Decrease conflict-of-interest