Not just billionaires, there's research showing that a high percentage of senior executives are likely to be psychopaths. Capitalist system selects for this behavior. People who are willing to lie, cheat, and step on others, are the ones that are rewarded and get ahead. Honest people with morals get filtered out along the way because they aren't willing to do what a psychopath would do to succeed.

https://www.forbes.com/sites/stephaniesarkis/2019/10/27/senior-executives-are-more-likely-to-be-psychopaths/