For some fighters, orgs/rule sets really do matter, and much like how people like Tito and Hughes relished their elbows while Wand and Shogun brutalized people with stomps and soccer kicks, for Cro Cop...
...it really did benefit him to be in a ring. In a cage, I could see Francis tiring/discouraging Cro Cop with clinching and wrestling against the cage with his size and then blasting him with punches. In a ring, on the other hand, Cro Cop would be better served with his TDD and his striking offense. In the end, though, it really comes down to who lands first, because Ngannou isn't the type of guy you can take some punches from, nor is Cro Cop's LHK the type of thing you brush off.
It wasn't a fatigue problem that caused people to drop from Cro Cop's body kicks, it was a "That fucking hurts!" problem
There's no "may" about it. If Ngannou lands a bomb, Cro Cop's going to sleep.
Randleman was a wrestler who surprised Cro Cop - and everyone else in the universe - with a punch and Hunt also lost to Cro Cop in K-1 in pure striking when he was fresh off of his GP victory. The Cro Cop that Hunt fought in PRIDE was injured (hence his shoes for that fight to protect his injured left ankle) and just fought stupidly and gassed himself by throwing the kitchen sink at him early and then trying to wrestle him late. Neither are the best indications of a prime vs prime match-up with Ngannou.