If Bitcoin remains PoW, they can still buy that vast majority of coins, but everybody will have a trump card.
You know perfectly well, that the overwhelming majority of people will never mine any bitcoins and will never be able to compete with professional miners, just like majority of people don't compete with professional miners of natural resources. What matters for the majority of people is
unique use cases. How the crypto currency came into existence doesn't matter for them if they have to buy it anyway, as long as it's a decentralized blockchain, distributed consensus and secure network - that's all that matters.