Tua and Tyson (prime both) would have been an excellent matchup - neither could claim height advantage as they are roughly same height. Both have explosive power and one-punch knockout capability.

Tyson has elusiveness (good defense) and speed besides. He should have beat Tua. Of course, as has been pointed out ad nauseum (and it is true) if anyone can get Tyson into late rounds there is always the possibility that Tyson loses heart. He expected to overpower and win early and did that well. Get past that and into more chess than poker and Tyson's a bit befuddled.

Regarding Lewis-Tua, Tua's loss was not due to him not being up and ready. It was due to Lewis' height, power and skill - using his jab to keep the shorter Tua outside his striking range, but always right where Lewis could hit him. Tua lost because Lewis won. Lewis didn't win because Tua lost.