One of the most horrifying things I know about humans is that almost all of us are susceptible to this and it’s not simply a matter of people kissing their ass, though that certainly “helps”.
This doesn't have to be true. I have explained to one of my kids when asked why I don't think the rich are good people.
Me: Well, what would you do with a billion dollars?
Them: buy lots of toys
Me: ok, after you have bought all the toys in the store, what would you do?
Them: Buy toys for all my friends... Well maybe they could have the ones I'm not using. Buy a house? Buy you a new car?
Me: What would you do after you had bought all that and still have almost all of the billion dollars left over, since a billion is so huge?
Them: um, buy houses for the people that don't have houses? And food for the people that don't have enough food?
Ultimately I believe that to have a billion dollars for any decent length of time you are probably a bad person, because even a kid's instinct is to use that money to help others', even people they don't know.
While wealth might make people bad as you imply, I think an equally valid option is that good people don't stay wealthy because they use the money to help others.