I think huge numbers of people can remember things the wrong way. Normally from not paying attention, or just not being educated on certain things.
Just an example. Nelson Mandela wasn't really that well-known worldwide. People likely weren't paying much attention to bits of news centering around him in the 80s. Maybe a lot of people mistook what they did catch on TV for a funeral. Or perhaps all people vaguely know about him is that he went to prison in the 80s and that he's dead, and those two bits of knowledge got merged into one false memory. At the end of the day, human memory is extremely flawed, and this is a more likely explanation than alternate dimensions.
I knew never died in the 80s, but I've noticed other examples of this effect.
I used to think Kit Kat was Kit-Kat because I never paid much attention, and to be frank, it makes more sense to have a dash present in that name.
It wasn't until my fifth or sixth viewing of the Star Wars trilogy that I realized Vader says, "No. I am your father."
I was spelling Skechers wrong for years because, honestly, the rules of the English language dictate that there should be a damn T present in that word.