This attack vector is dead after the 2017 failed attempted takeover. If you're not familiar with the subject there's a great book about it called the Blocksize War by Jonathan Bier, which you can grab for free as a kindle or audio book right now. https://www.amazon.com/Blocksize-War-Control-Bitcoins-Protocol/dp/B096CLR1SS

But even before we get to talking about forks and fungibility, don't forget that Blackrock and friends are at a major, major disadvantage here in Jul 2023. THEY DON'T HAVE ANY COINS YET.

For them to acquire enough coins to theoretically do what you're worried about, they have to drive the price of bitcoin up so high that the bitcoin community (today's hodlers) become rich enough to control laws & commerce on this piddly little rock they call earth. We'll be the power players before long if they try that, and then we'll simply tell them, "no."