There is no stopping billionaires buying bitcoin. Investor, businessmen, billionaires are all into money making potential. Bitcoin has gone to 20k which is multiple fold just few months ago. So not surprising they would want a piece of profit as well by jumping into the bandwagon.
Yeah everyone want to be rich even the rich people want to become more rich, a person will never say it that he is rich enough, so it is the main reason most of the billionaires are investing in bitcoin there is no restriction for them to use bitcoin, anyone can buy bitcoin and can invest at anytime, if the ballooners will invest in bitcoin it will make them millionaires very fast after the investment of one year or maybe two but it will make them more rich, several billionaires in my place are generated from bitcoin investment and I am also going to be rich soon with my bitcoin investment.