when i saw a company buy big amount of coin, i afraid.
I don't think there's anything to be afraid of when institutions have paid more attention to Bitcoin and the crypto market. The only negative thing about these events, in my opinion, is that ordinary investors will be able to afford less and less market shares. As the great interest of the institutions raises the price, and only they have huge capital with which to buy a large number of coins, ordinary traders with small capital will be able to buy smaller and smaller shares.
But as what OP speculates, that really be impossible. We could really feel the market manipulation but no one will think about destroying Bitcoin just for their silly ideas. I mean, no one could dare to do that like it for sure that these whales/investors are also milking crypto. Actually, they can easily make money here and that is why they will keep this alive.