I've just recently been noticing many examples of the Mandela Effect, and I've been watching quite a few videos on this lately.
There are more than a couple that are really getting to me. What could actually be the cause of such a phenomenon is beyond me. I do not have a clear explanation. No one seems to have a great explanation, but there do seem to be some theories.
One theory is that there are parallel universes, and everything that you know, past, present, future, is, has already, and is going, to happen.. Like a still frame image out of a movie, you can move to any reality and visit time from that still frame vantage point. This would mean there are an infinite amounts of copies of ourselves, (or unfathomable numbers) in many different locations, and/or possible dimensions. If this is possible, the theory is that you may shift to another reality without realizing it. You may die in one reality, then just shift to another simultaneously. If this were to happen, the idea is that every reality will have slight variations in the reality of everything that has occurred. If large populations were to move realities (from war?) for whatever reason because of a mass reduction of population, there would be many people that share similar memories, and experience confusion associated with the reality that their reality does not exist, and never did.
There are plenty of other theories as well, and they are all interesting. I don't know which one I prescribe to right now.
The one that hits me the hardest is the Ed McMahon Mandela, where I remember him delivering checks in the 80's from Publishers Clearing House, and toting the slogan "You might already be a winner". But of course this never happened in this reality, he never worked for them, he never delivered checks out of a white prize patrol van with red balloons, and a bunch of "cheesy" actors pretending to be excited... But there is plenty of "residue" around from this one. He even made a video right before he passed away rapping about it. Very interesting topic, very interesting question.
Some people claim that the Mandela effect is linked with time traveling, and that some time travelers, currently on earth, from parallel universe experienced different sequence of events. However, I think that the notion of the Mandela effect is usually promoted by individuals who prefer to believe that the entire world revolves around them. Hence, should they remember anything that is distinct from the perspective or opinions of other people, then the whole world must be indeed wrong, and not themselves. I think such people find it way easier to actually agree with claims that several parallel realities have crushed into one another rather than simply admitting that they made a small blunder.
The CIA could be responsible for whatever weird things the media made you believe about Nelson Mandela. The CIA was actually very threatened by Nelson Mandela and up until 2008 Nelson Mandela was on the US Terror Watch List: https://www.bbc.com/news/world-africa-36296551 see that article about him being on the Terror Watch List. Here are some more articles related to the CIA's interest in Nelson Mandela:
The CIA is involved in so many different ways to affect the media, they even have a say in what goes down in some Hollywood movies. Just see how they like to "meet" with people and "kindly suggest" what goes into the movie:
Our Brain, it makes all that illusion. It plays with our memories making us believe that something has changed when in fact it was always there, only that we do not pay much attention or maybe someone is traveling to the past with a delorean.