In Lewis vs Tyson, Mike Tyson's camp had him bulk up to a weight that was over his ideal fighting weight. Their thinking was that it would give Mike Tyson an increase in power against the larger Lennox Lewis. However, what it did more than anything was slow Mike Tyson down and make him a stationary target against the excellent Lewis jab. I think that there are some similarities in Fury vs Wilder and Lewis vs Tyson. Yes, Tyson was older and way past his best, but his weight gain made his odds even worse. Same thing, imo, with Fury vs Wilder. Wilder was slower and more stationary. (with that being said, I think Mike Tyson and Wilder lose the fight no matter what, but they could have made a better account of themselves by retaining their mobility)
If Wilder hadn't added the extra muscle though, perhaps his already heavily fatigued and struggling legs would have completely snapped under the weight of his costume?
I dunno. Wilder looked plenty fast enough when he decided to throw his right hand in the few times he did in rounds 1 and 2. He even Caught Fury a couple of times pretty good. Problem is, coming in lighter isn't going to improve his speed if he allows fury to rag doll him like he did. Wilder was exhausted by the end of the 3rd. Fury was fresh a daisy catching his second wind in the 7th.