Before Usyk entered the scene, Wilder was considered Fury's toughest opponent. In fact, many believed Wilder would win the fight, and he was the heavy favorite on sports betting sites. Wilder was -160 in the first fight and -125 in the second one. He was actually the underdog in their last bout, and he lost because Fury had figured out how to beat him. Although Fury had already defeated Wilder in their rematch, the last fight was a pretty dominant win for him.
Fury should not have a rematch with Ngannou, that is now in the past. Fury should be focused on trying to fight Usyk and trying to unify the belts to become the undisputed heavyweight champion (either that or Usyk will). He seemed to be on a decline after the highs of beating Wilder because he has been fighting boxers he was head and shoulders better than therefore a fight against Usyk just might make Fury elevate his game and enjoy boxing again.
Even though Fury won in a split decision, I dont think there should be a rematch. The problem was not because Ngannou is so good and can fight with champions on equal level, but simply because Fury underestimated him. If they would have a rematch I dont think that Fury is going to be so passive and slow.