Take it easy Op, the bitcoin market manipulations is not like that of the stock market where monopoly economy polices is practiced just to favour a particular trader.
For a billionaire to buy a million of bitcoins is possible as long as he has the money and while the supply bitcoin might not be sufficient to purchase such an amount of bitcoin considering the total number of bitcoin invented and the mined and unmined bitcoin, the Investors can always Dca in buying and accumulating gradually until he get to his limit of purchase.
Indeed Such value of purchase can cause a pump to the market when dump (hodl) but does not give the investor the hands to control the market because it is not a regulating market like the physical trading market.