What I don't see anyone here saying is the actual "problem".
Concentration of wealth is only a problem if those who have it, got it by means of some advantage over others not related to their own output. In other words, a good part of why they are wealthy is a benefit of an advantage given to them, that others don't have.
And today that advantage is corporatism.
Pick any medium to large city in America. 50 years ago if you drove up and down the streets, drove into industrial areas...drove in retail areas...everywhere. All of the businesses and factories you came across would overwhelmingly be locally owned and operated.
Today - pick any city. Drive all over it and most of the businesses you see, and what few factories that are left - are not locally owned. And there is a good chance the owner doesn't even live in your state let alone your city.
Now...drive outside of the city. Drive into much smaller towns. All the land around those towns used to be farms. Farms owned by local families. Most are gone. They cannot compete with the predatory nature and overwhelming advantages of Agribusiness.
Corporatism has turned millions of small businesses into much-much larger businesses. With far-far fewer owners.