In fact, to buy all the existing bitcoins will need too much money. One person will not be able to do this because it will take too many resources to accomplish this mission. It's impossible. But I agree that a very large number of bitcoins belong now to a small number of people. I think that this should not be so.
more precisely, bitcoin can be controlled by a group of people in a conspiracy. but it still does not exceed 40% because the distribution of bitcoin is evenly distributed
Currency is always synonymous with political affiliation, if one day bitcoin is legalized, then we can predict what will happen if there is a group in their country that has bitcoin at a 15-20% ratio, in my opinion, full decentralization is not entirely good for the future financial and real business.