I don't think bitcoin can be 51% attacked. However, it could be rendered unusable due to etchings on sats. Who would want to do this? If a state actor wanted to stop bitcoin from challenging the USD, they could simply print to infinity and buy rune block space pushing $100 dollar UTXO's with $10,000+ transaction fees. BlackRock could certainly manage this and they would be getting their own money back since they own the miners as well. The question is, how long could they do this before the USD is toast? Would love to see a math formula for that.

edit:
Or maybe Blackrock eventually ends up with a lot of the bitcoin if they pursue this avenue (in the form of fees). They were too late to corner the market. But what happens if the value moves elsewhere to where there's less friction? Then BlackRock has sent itself into oblivion.