Clubber punched himself out because he let Rocky get into his head, which lead to his fatigue.
Clubber was super strong and would wear down Drago at a faster rate than Rocky did, without having to take as much punishment.
I dunno breh, Clubber/Rocky was basically a mirror match. A good, small swarming fighter never beats a good, big rangey fighter. There's no way for Clubber to not take as much punishment. Head movement can only take you so far when trying to close a gap that big. He'd have to eat jabs and straights all night to do his work.
Now if the fight is in the US and Drago has to consent to USADA testing for an entire training camp then maybe you got something. But if Clubber got outsmarted by autistic Rocky then what kind of scheme psychological scheme are those Soviet scientists gonna cook up for him? Drago was state funded, he's gonna have to deal with a mental attack prepared by a think-tank of the Soviet Union's leading behavioral psychologists. Clubber got too many things going against him.