I can perceive demonic activity in relation to the Mandela Effect. Demons use different philosophies to deceive people, and entire religions. A lot of demonized people are idolaters or have at least dabbled in the occult. I can perceive something demonic behind at least one of the promoters of this theory that I heard online.
The theory was started, apparently, by a woman who tries to communicate with ghosts, someone the Old Testament forbade god's people to consult.
If people believe in the so-called Mandela Effect, then demons can use this to really mess with their mental health, their grip on reality. I've read about people seeing words either change on the screen or change between one websearch and another, but I think this is just demons messing with them to get them to believe in this nonsense. If Christians believe in this, then they can start thinking the Bible has changed. There were people who got Bible translations mixed up. They'd take verses I knew people often misquoted in the 1980's and say when they were a kid (in the '80's or '90's) the King James version said 'wineskins' but look here, it says 'bottles.' The KJV said bottles in the 1980's, and the NIV was popular and preachers would read out of the KJV and then say 'wineskins' when they preached. They'd take verses I heard misquoted in the 1980's or 1990's, where the popular quote did not line up with the actual text back then. They argue that the Bible used to say the same as the popular quote.
The strategy behind this is clever. There are so many things we don't pay attention to, like a little mark on a Ford emblem, the spelling of Frebreze and Fruit Loops. Probably a certain percentage of the population would think Frebreze has another 'e' in it if you asked, or the Berenstain Bears is actually spelled like a familiar last name. That's just how we process information. That Star Wars movie line was quoted as 'Luke, I am your father" in Tommy Boy. If the actual film said 'Luke' and they put in another sound clip that says 'No, I am your father" for re-masterings later one, there is no way to track it because you can't see Vader's lips.
Most of these effects are about things that people did not know intimately well. I saw one of the videos that showed that South America was so much further to the east than I remembered. But I am not a cartographer either. Then I saw an old map of Risk, a game board I spent a fair amount of time staring at as a child, and South American lined up with how I remembered. My idea of the map was influenced by Risk and probably some over simplified maps from a few video games.
Anyway, you can throw out 100 things most people remember or process wrong, then tell them reality is fluid and your mind is shifting between alternate universes. If you just found out you thought Febreze was spelled differently, that might be a little shock to your psyche, but just a minor one. Multiple that by 50 or 100, and you can have someone questioning reality. I believe this is just a clever demonic strategy. While this is going on, they can work on a person's mind and perceptions.
This is also the kind of thing that would emerge after the Internet was developed, because now there is a platform for regular Joe's to release conspiracy theories like this and get a following of tens or hundreds of thousands of people. That wasn't the case when only a relatively small number of people had the dedication, drive, resources or talent to get a publisher to publish their book, or when you had to pay a lot of money for TV, radio, or print ads. People can post their theories on YouTube for free and say they remember something different and blame it on the so-called Mandela Effect
I haven't looked into the missing building thing. I looked at some videos of this when the thread was first posted, and I've wasted too much time on it already. I don't plan to look into this more unless I want to help people deceived by it.