As we have seen, Kaido is always in a drunken state every time he shows up. I feel like there needs to be a reason for Kaido being suicidal and a depressed drunk. I think the real reason is Joy Boy, Kaido was obsessed with Joy Boy.

I think Kaido’s obsession with Joy Boy stems all the way back to his time with the Rocks Pirates. Maybe Rock D. Xebec brought in Kaido because he thought Kaido would be Joy Boy, but when it was later revealed that wasn’t the case Xebec was disappointed in Kaido.

This would explain Kaido’s depression and why he has occupied Wano all this time. Kaido knows Joy Boy will come to Wano, and wants to face him to compare himself to understand why he isn’t Joy Boy.

Well, it’s been 25+ years of stagnation… standing still because there is no move you can do to make the purpose you’ve found progress. That will make a man depressed and suicidal. I think it makes sense like whatever he does, he won’t find a worthy opponent until he meets Joy Boy. And he needs Joy Boy to feel progress in his life.