You can look at any other asset. Look at Bezos and his stock. It is the same, he can flood at any time the market with his shares and maybe break not just AMZN, but all markets of the world.
Now the question is: why should he do it?
Those unnamed whales, who are they? Most likley some idealistic cypherpunks, who live like me with computer, glass of water and cat. Maybe they could in fact start an attack on world economy, because they are pissed off, but... in fact they need money much less than Bezos who has to pay off his exwife or private jets.
What you are missing is so called marginal propensity to consume and marginal propensity to save. The richer people are the higher is marginal propensity to save. I am saving maybe 99% of income for example because I have money. (But my rule even when I was poor was to save 95%. I was homeless because of that. The way to make money is simply not to spend.) The BTC whales do not need to spend the money.
Same thinking is when you are driving and maybe you think: what if I turn the wheel at the curve a bit. I will be dead. Yes, you can do it, but you will not. Same problem is what POS coins are (not) having: if whales decide to disrupt the coin, they can do it much more than by POW coins.
I understand psychologically the fear of unknown powerful someone. But it is a fear that made sense in deep forests. Now we should be afraid much more from known powerful entities: like politicians, central bankers and even more from society. Society can and does and will force the cantral bankers and politicians do the same that you fear of whales. They are and will disrupt the money and the economy. Because they must. Because society forces them. The whale 1. does not need that much money for consumption 2. even if the whale wants the money, it wants to offload without disrupting the market to get the most value out of it.
If you talk to God, you are praying; If God talks to you, you have schizophrenia.