They coined it the Mandella effect for the same reason you mentioned above EL P. Apparently a bunch of people thought he had been dead for years and when his death made the news they were confused. One stupid lady even called into the Howard Stern show and said he was a great actor, really awesome in that impact movie, she was sad he was gone .
I love the idea of a multiverse but when it comes to the Mandella effect IMHO I think it is a bit of a fake rabbit hole to play with, its a representation of how our memories actually work and the idea that they are concrete is far from the truth. I think the implications of it can scare people so we would rather not acknowledge its truth. Everyone thinks their memory of certain events are the Bees knees, until they talk to someone else that was there and realize they have conflicting stories. One of my friends even retold a story that happened to me as if it happened to him. It was pretty crazy, he told me the story one day and It was like, uh what the frick are you talking about that was me. He was so sure I was wrong he required a third opinion from another person that was there to convince him. "haha oh man that's crazy, I have been telling that story for years"
Watched a few show's where they try to show that our memories are not what we think they are. The phrase they used that stuck in my head was you have to understand that my questions can pollute your answers. So when I asked you if you remember the berenstain bears or the bernstine bears, it is essentially a loaded question that manipulates your memory, or lack thereof, before you even get to really think about it. They used examples like at the scene of an accident if you used the phrase hey how fast was that speeding car going? They found eye witnesses would increase their perceived rates of vehicular speed. There is a false assumption of quickness asserted there in the question that works it's way into the answer.
I think that mechanism may have something to do with the odd time the police seem to elicit a false confession out of someone after badgering them for hours
Another experiment they did was to prove that you can load someone up with a false memory if it gets worked on. In the study they took 20 or so participants and asked them to recite say 10 random memories from when they were young. Then a week or so later they asked the group to come back and they read the stories back to the participants. The catch being the scientist inserted a totally fake story that they claimed was volunteered by the participants parents via a phone call. At first most of the participants would show some resistance, but when they continued to ask them to try to remember the wheels slowly started to turn. Even by the first day some participants said they thought they could actually remember the story. With more time the majority of the others started to "remember" and even fabricate more complicated details. After coming back on the third or fourth week they could now remember the colours of clothes and other details that never actually existed.
For the record, the story was that they got lost one day as a little kid in the mall.
One way they try to explain this phenomenon is that your memory is a bit of a creator. You remember a rough outline of a situation for efficiency reasons and then when you remember it your mind fills in the unnecessary information to make it complete scene. Good examples would be stuff like colour of clothing or the exact date it was on, the time of day, ect. There are very few people alive that have access to that level of detail for every single event in their life.
A good visual representation of it was to think of a memory like an ice cube. When stored it is frozen, but when you pull it out and start to work with it the memory becomes soft and malleable like a melting ice cube, and the more you play with it the softer it can get and it starts to change shape
A sad instance of this was a case of rape. During the rape this woman told herself all she could think to do was to remember the guys face, focus on his face and you will never forget it. Flash forward to inside the police station confronted with a line up of suspects and she was not able to make a clear distinction between two men that she had narrowed it down to. Eventually she made a decision and the Judge said it was one of the fasted court cases ever. As time went on she became more confident in her decision, the woman's testimony was so credible the jury had no problems finding him guilty. The decision was all based on this credible eye witness account. I think he was in prison for something crazy like ten or twenty years before he was exonerated on DNA evidence and found innocent. Now they even use this as a reference to try to discredit eye witness accounts
I wish I could find all those videos and post them to further illustrate my point, one could guarantee that my recollection of it all is going to be a little off