Mandela effect

Back in the dark ages when I went to school, we learned that Abraham Lincoln's famous Gettysburg Address starts with the words:
Fourscore and seven years ago, our forefathers...
But now, if you go to the internet and look it up, you'll find that almost everywhere it has changed to be fathers instead of forefathers.

However, I have found a couple counterexamples where the original forefathers is used:
  1. radio drama
  2. Johnny Cash
Amusingly, in the first one, after setting up an elaborate joke based on the word forefathers, Charles Laughton then goes on to recite the address with fathers instead of forefathers.
The two counterexamples prove that I'm not losing my mind, I really did learn it as forefathers. It seems that someone has gone through the entire internet and altered the speech. This has been done very skillfully, so that it is impossible to see that anything has changed. In my first counterexample, the speech was changed, but it was impossible to change the preceding dialog to obviate the word forefathers. In the second one, my guess is that the song was not even recognized as a recitation of the address. Or, if it was, then changing the song was beyond the capability of the changer.
How and why was this done? My guess is that it was done by AI, and it was done simply to prove that it could be done. Personally, I'd like to see the Lincoln Memorial, where it is carved in marble. Also interesting would be any photos that people have taken in the past of that memorial.
Perhaps all of the many Mandela Effects have been done similarly by AI. Maybe they were done simply to confuse people, to be grist for the mill of the conspiracy theorists, something to keep them distracted.