The concentration of power, in this case, refers to political power not market(economic) power. If you think about it carefully, economic power often is very weak and vulnerable as they often derive them from consumers which means they can only maintain it by giving consumers what they want. People like Bezos, Bill Gates are far less powerful than say, Putin, Erdogan, Xi, etc.

As an example, how far did Bloomberg's billions take him in the democratic nomination?