I'd be interested in the next few sentences to go deeper on why. Why should we delegate the prioritization of societal values to the wealthy? what about wealth-accumulation makes them better suited to choosing how we should solve problems for our society. And why are you and I not equally responsible for influencing the direction of things within our means?
I wouldn't say that Bezos has an obligation to maximize well-being any greater than ours; but as the other comment pointed out, he is uniquely placed to have a much larger impact on large-scale problems. You're absolutely right when you imply that he is no better suited than anyone else to become an authority on those problems. And I think we are morally responsible for influencing problems within our means. Bezos can fund public libraries and provide clean drinking water, whereas I can comment on HN with a rudimentary understanding of meta-ethics :)