Countless times we have seen people starting good and ending bad. On the way up, they have accumulated power and lost their ground and moral.
One can say that there are powerful people who remain human. Yes, maybe there are. But they need to have strict rules and follow them. Ask those people what their rules are? (Ideology) What do they believe in? And occasionally remind them of their own rules.
The people from the history books also thought that they ware ok. We are all humans and vulnerable. We need rules and reminders. Especially in the face of power.