Every single metric shows that the wealthy are increasingly effective at concentrating their wealth. This has been the trend in the United States since the mid-20th century. It's undeniable that they are deliberately and effectively doing this. The only question is whether or not this concentration of wealth is good for society or bad for society. Due to the complexity of societies, this is difficult to demonstrate empirically. I grant you this.
If you think that these conditions haven't generally lead to the formation of strong kleptocracies throughout history... well I guess we'll simply disagree.