Y'all do realize, this story didn't start at Isekai, right? Bandersnatch wasn't established in a single day, Chataeu Gothika built the very next, and then Rodias was hit by the Isekai Truck.

The NPCs aren't JUST NOW realizing they have neighbors. Assuredly, Chuunitrixx has been with Traptrixx to loiter in other Chapters and Facilities. Same with other NPCs; they gained sentience, not location amnesia.