Joe in his prime was incredible fighter
He ran in to the problem most short heaveyweights run in to,he got old real fast.
Shorter fighters need their legs,and thats the first thing to go,they need to be able to explode in.Once the explosion's gone,so are they.
Tyson had the same issue,compounded by the fact that he refused to learn how to fight any different then he ever did,once some fighters proved they could take his best punch,the jig was up.