There's recent precedent (Pereira-Adesanya 3) for a specialist KO’ing a 200+ lbs (on fight night) UFC lineal champion, who was P4P No.2. There's also precedent for a boxer beating a former two-time UFC HW champion in an MMA fight: a 20 lbs overweight and shot beyond belief 48 year old Mercer (who wasn't even a KO artist in his boxing prime) iced the previously un-KO'd 33 year old Sylvia with one punch, in 9 seconds. Let's say the first fight is a boxing match and Wilder (who was able to land big on 6’8 master boxer Fury) KO's a slow and defensively open Ngannou early. In the MMA rematch Wilder would have a huge advantage, with the previously un-KO’d, now 37 year old Ngannou terrified from the opening bell (partly because he wouldn’t want to be humiliated by an MMA neophyte) and carrying some additional physical wear. Ngannou mentally collapsed post-Miocic 1 (a fight where he wasn't even finished) and subsequently fought scared against a less rangy, less athletic, MMA KO artist in Lewis, losing a decision. In an MMA fight Wilder would be wearing 4oz gloves, increasing his already monstrous power and there's no 10 count, so there's a great chance that the fight ends with the first knockdown. Wilder knows that he couldn't afford to let Ngannou wrestle him so he would go for broke early, which is also when fighters are most vulnerable to explosive punchers.