Because, as Yamato confirmed, Luffy is barely standing due to previous fatigue and damage that he obtained when he was weaker than he is now.
Kaido didn't have to start taking adv CoC blows until chapter 1010, anything else is basically zero damage to his dragonic zoan physique.
Luffy's "sloppy usage" of adv CoC for 30 minutes drained him tremendously as he isn't used to the ability, Zoro with much weaker levels of output could only last a few minutes, and that drained his life force.
Luffy isn't fresh... He was explicitly singled out by Yamato as more nerfed than Kaido, and that is common sense, Luffy is just learning adv CoC, and doesn't have the benefit of a mythical zoan regen/damage soak. Luffy has been knocked out multiple times and Kaido hasn't.
I really don't understand how you can have this copium.