[x1000]

An interesting aspect of these cryptocurrencies is the aspect of consensus, not through the intended mechanisms like PoW, but through societal acceptance. Look at BTC and BTG (bitcoin and bitcoin gold). One has the suffix of "gold" while the other maintains the (arguably?) superior lack of any such embellishments/augmentations. Was it the miner's decision to call it that? Was it the users?

Look at Ethereum v Ethereum classic. Same deal. We have two chains that share a common history, yet at some point the users of both decided to split and then society had to come to a consensus on what each chain would be called. Again, did the miners sit around and conspire to which chain would be called "Ethereum?" I don't think so. I think the decision was decentralized and emergent.

My point is, even if there was a nefarious actor who attempted a 51% attack, it seems like there would be enough of a societal pressure to ignore their empty blocks. There would exist a chain that would still be valued by the perpetrators, but not so much by the individuals being harmed by such an attack. The attacked chain would be maintained and acquire a new name "Bitcoin Hacked" or something similar, and the chain where society ignores the empty blocks would go on its merry way still being called "bitcoin."

[habitue]

I take the point you're making (in principle, there is some off-chain consensus at work here), but for these particular examples I believe society didn't decide these names as much as the people deciding to do the forks did.