I would like to see a source for this. The hyper-wealthy may not spend as much money on food and shelter as a percentage of their wealth but they invest massive amounts of wealth into innovation and spur further economic growth. They certainly don't hoard wealth and have money just sitting there collecting dust.The growth of billionaires is a problem for two main reasons:
1. Such concentration of wealth is a very inefficient allocation of national resources. The hyper-wealthy simply do not spend enough of their money to turn the wheels of society. The golden age of western societies corresponded with periods of high taxation and redistribution of wealth driving demand from the middle class.
Well, that is more a problem of governmental structure than it is of wealth accumulation. Keeping the people poor so they cannot challenge your authority is putting a massive handicap on your private innovation capability. Rather, China's system has so far been very effective at making itself clear that your wealth is dependent on your allegiance with the government and the national interest.2. It is a political challenge to the authority of the CCP, and more broadly to any form of government that seeks to employ rational intelligence in service of a broadly construed national interest. Wealth is power, and those with wealth will seek to use that wealth to advance their own interests which do not necessarily correspond with those of broader society. See the Wall Street plot to overthrow the American government in the 1920s.