I don't know why people are knocking David Seaman over this. The "Mandela Effect" is easily explained by the media innocuously publishing what later turns out to be a legitimate mistake. The media gets lots of stuff wrong, they incorrectly announce an actors death when they're very much alive. Maybe some paper did that with Mandela in the 1980s and some people saw the story and never saw the correction. Or in the case of the Bernstein vs Barenstein Bears someone probably wrote an article on the Bernstein Bears and then had to correct it.

The point being when the media does that large groups of people get the story wrong through no fault of their own. It's just part of being human. No conspiracy, it's just fascinating the stuff that gets mistaken.