I recommend reading up on why these observatories and telescopes are where they are in the Atacama. It’s not just about the lack of light pollution, it’s a specific geography that “smoooths out” the air. Something about the high elevation prominence coming up directly from the coast creates a unique situation that allows for longer exposures, something that is less possible out in the open ocean. The only other comparable place are the high peaks of Hawaii, but these are mostly off limits due to native protections.

Destroying an aspect of the dark skies in Chile will absolutely hurt astronomy. No, they would not just be able to move their operations out onto a different mountain range or into the open ocean.