I think you have to be evil to become a billionaire. Nobody by themselves contributes something to society that is worth billions. So they are taking more than they contribute and are apparently willing to do so and disadvantage other people. This is evil. That is why there are no good billionaires.

Also, if by some extreme coincidence you become a billionaire by accident and if you are a good person, you would give it away for the benefit of society. So then you would not be a billionaire anymore.