He lost a lot of weight for Fury Vs Wilder #1
Felt weaker, didn't win on points, fired his young coach.
Went back to his regular routine, gained the weight back, smashed Wilder on #2.
I think we shouldn't judge just on look when it comes to strength and power. Fury is totally ripped under that flab, that is probably needed to feed him that extra energy and punch weight.
I recall an interview were Fury said he saw quite a few defense weaknesses in Wilder and he made a conscious tactical decision to keep Wilder under pressure in the F-W2 fight ..