Muhammad Ali hits his prime in 1978. What happens next?

Whoa, Nelly. Let’s begin in 1978, Tyson is still ten years off his own peak. In ’78, the spectacular four-year reign of the invincible George Foreman comes to an abrupt end, ala Liston in the real timeline, as the 22-year-old upstart from Louisville shocks the pundits (having been dropped in his previous fight by Chuck Wepner). Ali beats Foreman again in early ’79, & at about that stage, Larry Holmes is ready to challenge for the belt, fresh off his win in a barn burner against an ageing Kenny Norton.

It’s a great back & forth. Holmes puts up the fight of his life & catches Ali a little too full of himself, & Holmes snatches a narrow decision. Ali, the better fighter overall & humbled by his defeat, decisions Holmes in turn in June of 1980. Holmes stops Foreman late in December of that year, & the latter announces his retirement. Ali keeps busy with highly overmatched, mostly past it contenders (due to a lack of big names & consistency among the young crop) like Jimmy Young (UD15), Ron Lyle (UD15), Earnie Shavers (TKO11), & Gerry Cooney (TKO9).

Holmes beats all comers too, & can’t be denied forever, so a trilogy results in a razor thin, a few argue controversial decision for the more popular Ali in January, 1983. Ali regards the Holmes business as done. Ali continues on as Champ - staving off Holmes, who loses unexpectedly to Michael Spinks. Holmes win his rematch in March of 1985, but can’t wrangle Ali in negotiations for a fourth bout before he’s shocked by young Mike Tyson in 1986. Tyson continues his development through to ’87, when public pressure reaches fever pitch. Lack of public support sweeps Holmes aside & into retirement. Ali wins the press conferences with young Tyson, but does he win the fight at 30, fourteen years into his pro career? He’s just good enough. Tyson handles the loss - in which he had Ali down & in mortal danger in the fourth - poorly, until he’s brought undone by Buster Douglas, just as Ali drops a razor-wire decision to Evander Holyfield in early ’89.

Ali retires as a two-time Champ, & while a minority regard him as the greatest ever, he’s now majority-second in most peoples’ eyes behind Joe Louis.