MOON SIZED AI?
Not necessarily, its a orbital platform and likely in a much closer orbit that the Moon itself so appears "bigger" as I dont think I would need to explain why.
It also appears to be larger that the Moon itself, its another indication its closer, not bigger.
Also I dont mind that since if this is Earth in the distant future of the year 1992 (I wonder how many will get this reference) then where the second moon come from? The Moon is somewhat rather unique being its about 27% of the size of the body it orbits (Earth) and satellites arent usually that large compared, Ganyade is the largest moon on the Sol system but Jupiter dwarf Earth by sheer size.
There are a lot of unexplained things in this world as it mostly just gone about the Quest to Defeat the Demon King, will they be answered? probably not as I suspect at first this was done as a Isekai before he decided to make the twist being set in Future Earth but at least he is going to go about things that is fine, the 2nd moon was very much turned into a red herring nut its worth explaining since as we know its future Earth were the hell did it even come from.