Power begets justifying why one has power. The American system invites people to amass not just "due rewards" for their efforts, but nearly godlike wealth, influence, station, and power. Often not for anything that can be rationally reasoned as a direct result of The Sweat of Their Brow.
Those who godlike power and station in a society, regardless of how they got it, regardless of how 'just' it is, tend to fall into a basic trap of human psychology. They come to believe that they have what they do because they're just different from other people, which tends to quickly slide into "they're just better". The drudges are the drudges, the poor the poor, and the elite the elite. So it was written, let it be done, amen.
And when people live like royalty compared to the average person in their society, they tend to fall into pattern of royal behavior down through history.
The good side of the American system, and similar systems, is that it does at least offer the potential for some people to achieve the godhead truly coming from humble beginnings. And there's a chance those people will retain perspective against even their own psychology whispering their ear. I think this is demonstrated in the shape of the sane, responsible, wealthy individuals in the US - you know, the people who break rank with big money and say "tax me more".
But the problems of power remain, despite that mitigating factor. There's still plenty of capitalism-built royalty to go around.