Let's imagine that them and few other whales bought up all the supply and the price skyrocketed to $100k, then what? Are they gonna sell&buy it from each other? Bitcoin will become is a very expensive asset in the hands of the few, no mass adoption will ever happen. Maybe that's their plan who knows. There are many very rare earth elements which are much more expensive that gold or platinum so what? Not many know and use them.
The fact is that big Whales already receive quite large incomes, including paypal. There is some opinion that big whales, including paypal, will be able to maintain the value of Bitcoin at the highest level, thanks to their capital, without allowing a fall in the landfill. Perhaps they will achieve a situation where most of the small Bitcoin holders sell their assets.