Why would it be an off night ? It was arguably the biggest fight in Holmes's whole title reign. And looking at the fight it was apparent Holmes was in shape and sharp. Based on Cooney's galiant effort going 13 rounds vs ATG Heavyweight at his best, and the fact he dismantled some known fighters in a single round, yes they were past their prime but still solid wins. Also the fact Cooney's power looks very impressive on film especially body punches for a big man, H2H it seems quite feasible Cooney would be dangerous at his best.
I am not saying that it was an off night. I am saying that we can't be sure it wasn't. Hence it is dangerous to rate Cooney highly head to head, based on this single performance.
Well it clearly wasn't though ? The footage is there for everyone to see. Holmes was sharp in shape and highly motivated. Stoppages over Norton, Lyle, Young, are not to be scoffed at either, even if they wern't at their best still decent wins on resume especially how Cooney beat them.
Holmes was angry Cooney was getting all the attention,he trained hard for this fight ,and was in top form.
I don't think anyone is rating Cooney all that highly, head-to-head. Against Carnera, you don't necessarily need to be.
Then I will offer you another option, that Cooney might simply have been a stylistic foil for Holmes, but not much else.
Ok, so now you theorize Holmes wasn't having an off night, but was instead made to look good by Cooney (who himself exceedingly performed well)? Forgive me when I suggest that you seem to be arbitrarily plucking ideas out of thin air, without taking the actual action of the Holmes/Cooney fight into consideration. And, as alluded to earlier, the Holmes/Cooney bout was fought at a markedly superior level to anything Carnera exhibited. Had he ever looked like being a competitive a threat to Louis when they fought, I might think differently - but Carnera was thoroughly mugged by Louis, punctuating the reality of his level amongst heavyweights.