The most obvious suggestion, which is called out in the article, is that the author is simply lying; that none of this happened as described. Personally I find that explanation far more likely than gaslighting, schizophrenia, sleepwalking, or haunting. Absent independent and trustworthy verification of the events, that is my default assumption. It's not unfalsifiable, but it is where I start with stories like this.

Isaac Asimov wrote a very amusing Black Widower tale along these lines--The Obvious Factor--that significantly improved my own rationality. Briefly, that story taught me and to this day reminds me that you cannot simply accept first person reports as evidence of implausible phenomena. It may be impolite to state this so boldly, but surprisingly often it is useful to at least say to yourself silently, "I do not believe this person is telling the truth." Even more so on the Internet.

While most people are truthful--i.e. describe reality as they remember and recall it--amongst that fraction of people who tell wild and exotic stories, the percentage of outright fabulators is much higher. Given the prior of a ridiculous tale, I adjust my probability that the teller is a liar way upwards; and I'll continue operating under that assumption until I see independent evidence of the claims.

I'll put forth a hypothesis here: this story is simply a thought experiment to see if it's possible to envision a scenario in which "objectively irrational beliefs can, in fact, be subjectively rational."

Or other psychiatric disorders that can involve psychosis.