It was a lot easier to do back in the day then it is now when everything is so easily documented, photographed and logged. You could rewrite things to make them fit the new narrative and people would accept it. It was a lot more effort to go back and look up what really happened and the new version was accepted as truth. Would it work on kids though? It should be even easier they hypothesized and decided to screw with parents of kids at the same time.