For purely practical reasons, we should make efforts to disperse power within society away from severe concentrations. Not uniformly, not absolutely, but we should work to keep the trend from becoming too strong in the direction of concentrated power. Otherwise, the vast masses are liable to suffer and experience reduced capacity to alleviate that suffering. See: All of human history

What is this argument even?

Some people are more influential than others. Money is only one vector of influence. He's rhetorically asking whether we should regulate the other vectors with hope that no one person has more influence than anyone else.