Foreman did well trying to put his name out there when he came back in 1987, he created a huge hype's machine behind himself, and Tyson obviously was the guy to call out since he was the man.
Tyson also was considered somewhat similar to Frazier, by many that don't know what they're watching, so lots of people thought that Foreman had a chance. Add to that some propaganda's articles by insiders, and you had all the hype behind a possible Tyson-Foreman's matchup, with the rumor that Tyson was scared.
Now, i don't know if Foreman would've took the fight or not, seeing how he carefully picked all his opponents and avoided the big guys, probably not unless huge money. What's sure is that he had no chance whatsoever in that fight.
Foreman, who was a bigger, stronger and a better fighter when he came back, compared to his 70s caveman, lighter and green version of himself, was really too slow to compete with Tyson, and not athletic enough.
No heavyweight before Tyson's time would beat him, especially punching-bag Muhammad Ali. Tyson was too fast, too technically sound, too strong, too athletic and hit too hard for the limited guys from the 70s, 60s and before.