I mean, let's go further than that even... Imagine if somebody invented commercially viable nuclear fusion and achieved effectively free and infinite electricity, then by your logic, either of two things could happen:

- Bitcoin becomes immediately worthless, because suddenly many actors could afford to tap infinite energy to mount a 51% attack and destroy the security of the network

- Or, self-interested miners would try to "corner" the market, nearly infinite though it may be... Industrial players might try to outrace each other in terms of bringing more fusion power plants online that are dedicated towards mining -- "white hats" trying to preserve Bitcoin, vs "black hats" trying to destroy, and it's just an arms race... Maybe the end result is actually that, humanity only has productive need for 5% of the total energy that fusion generates (hey it's my thought experiment, just go with it), so what do you do with the other 95% that is otherwise pure excess? ... Maybe it all goes back into Bitcoin mining anyways, because maybe God loves a recursive joke