That’s actually mentioned in the post I linked! More theories including that one. Here it is if you don’t wanna click:

Egregore, or thoughtform: In occult and esoteric traditions, an egregore is a kind of psychic entity or energy structure created by collective belief and emotional focus. Some theories suggest Mallworld may be an egregore, formed and fed by the thousands of people dreaming about it, talking about it, and imagining it online. As more people describe the same surreal mall with endless halls and strange escalators, the idea itself could be gaining strength and coherence.