Moorer was a warm favourite. It is possibly not up there with the biggest upsets in the Heavyweight division, but I do not remember anyone picking Foreman to win. The only debate I had was if Moorer could get the retirement win rather than the easy decision.
"The only way Moorer can lose, Atlas says, is if he is tricked into giving up, just as Muhammad Ali tricked Foreman out of the title 20 years ago in Zaire with the rope-a-dope plan that succeeded brilliantly." (Los Angeles Times) To me Foreman's win is very overrated and i think Holmes' Mercer win was better.
I recall Moorer being expected to win easily. But I also remember thinking that Moorer was a bit chinny and that Foreman could potentially take him out if he landed a "lucky" punch. But I certainly didn't bet on it happening. Not after the Morrison loss and subsequent year and a half of inactivity. It was supposed to be an easy money fight for Moorer.
I remember back then there were talks of a potential fight between Micheal Moorer vs Lennox Lewis to unify the titles shortly after Moorer beat Holyfield. Talks never materialized and it appeared as if Moorer wanted a quick low-risk payday before taking on bigger challenges. Foreman was chosen specifically because he represented a nice payday for Moorer with little risk. Nobody expected Foreman to win, nor was he viewed as a legitimate threat. People respectfully gave him a punchers chance but prior to the fight it was seen as being charitable. Don't get me wrong it wasn't Braddock vs Baer or Clay vs Liston or even Tyson vs Douglas, at least not on paper. But it was a long shot.