If you are underestimating your opponent and using sub-optimal strategies then you are off full guard.
"A lioness will use all of her strength even when hunting a rabbit ", well Kaido didn't do that by sloppily using a slow charge up attack to finish someone on deaths door, when he had faster attacks or other means that would have eliminated any risk to himself, he thought there was no risk and was surprised when he got tricked by Asura's illusion and damaged by Zoro's base CoC+ Enma's potency.
Luffy getting tagged by Apoo and caught by Ulti is a similar analogue, actively not using future sight, not using ryuo, not using his fruit properly to escape Ulti's grip. Just sloppiness for plot sake.