They can have big shares in Bitcoin circulating supply but control the network, they won't have that power.
Black Rock started to show something big in the last year by investing in 4 of 5 biggest Bitcoin mining companies.
BlackRock is a major shareholder in 4 of the 5 largest Bitcoin miners. And they also spent their resources for Bitcoin Spot ETF application against SEC. Finally they succeeded and they are buying a lot of bitcoin last 40 days. Already surpassed MicroStrategy as a biggest public company holds Bitcoin.
https://bitcointreasuries.net/
That's what you think, now let me tell you a little about what control is all about, Blackrock doesn't need to own the blockchain or claim bitcoin to their name or even have the power to change the way bitcoin has been operating but all they need to do is have enough power to influence the market, price and if they ever get to own enough bitcoin they could well start controlling supply and demand of bitcoin and as we know it or decided to turn a blind eye on it that is their aim and don't think big players come in to be benefactors they come in to have power in the game and soon that power would forever leave the hands of retail investors to their hands or rather It has already left long ago, remember when Grayscale literally caused a dip by selling massively didn't that give you an idea of what they can do owning such percentage of bitcoin. From this moment on we should have in mind that bitcoin can be manipulated, and don't think Blackrock just had interest in bitcoin without having some motive of their own, think again.
I'm afraid that this might result into actual manipulation where in we've been talking about manipulation years ago and now this might come into reality that we know some institution that can actually do the thing.
Like someone who actually gets this, very soon it would big players vs retail investors and I Don think we have that power to play that game, they could cause a dip that can shake everyone's hands and raise the price up so high, just by manipulating the supply and demand of bitcoin besides that have the quantity to do so.
The only way I see that this might not happen is if they are afraid to lose their holdings to other big players that would be more than ready to by what they have sold. That way we could have quite the balance but this would only work when they are two companies have equal shares of bitcoin or almost same amount.