If you suffer one of the worst upsets in history, it doesn’t mean that the person who upset you, is automatically a factor against the great fighters who took care of their business!
I'm not sure any of Marciano's opponents ever performed as well as Douglas did against someone as good as Tyson was.
50/50 Douglas fought the perfect fight to beat a come forward pressure boxer that night. I reckon beating Tyson is more changeling than beating Marciano.
Marciano beats the count in round ten and finds his mark in round twelve. Some guy just won't stay down.
In spite of Douglas' physical advantages over Marciano, you may be right here. Quite frankly, if Tyson had maintained his once impressive training habits (something Marciano never considered abandoning) he would have probably found a way to stop Douglas on 2/11/90.
Douglas knew how to fight the shorter man. This is a fight where it is entirely reasonable to favour Douglas. Of course, Marciano might spark him out sometime too.