Not “an alien” instillation, but hundreds on both sides of the moon.
Besides there is nothing to say the putative installations are not a human or at least a previous Earth civilization we no nothing about.
More over there are many formations on the moon that have no geological explanation of their formation.
The lunar surface was made the way it is by impacts. The only artificial things there were put there by humans in the past 60 years. That makes sense, since ETs would have little reason to build there and not here.