Do they have great faith in bitcoin or are they trying to make bitcoin their own game because like you said they can manipulate the price of bitcoin if they want? It's really hard to know what they're planning with bitcoin when they buy such a large amount.
Overall, Blackrock's massive acquisition of bitcoin has its pros and cons, and it's understandable that people are concerned. But at the end of the day, there's nothing we can do to stop them from buying bitcoin. For example, today the price of bitcoin suddenly dropped to $68k and some ETFs like ARK, Fidelity or Bitwise sold but Blackrock continued to buy a large amount of bitcoin. Today alone, they continue to spend over $300 million buying bitcoin and they don't seem to care about the price of bitcoin or what the market is doing. Should we be happy or sad?
It can be both because there is also no sense of buying it if you can't benefit on it. Though, I remember that even a shitcoin can also be manipulated. It only needs some hype but at least in Bitcoin, if they fail to manipulate it, they still can earn.
BTC is truly hard to manipulate due to its less supply and a lot of people are holding their coins tightly because they also believe on its potential and they already know that the coin has a lot of value due to its other features and usefulness. Scaring them or spreading a FUD is no use on stopping them. They are not kids anymore but I think the only best way is if the government bans BTC on their country. A lot of innocent people are going to get affected by it though.