In Chapter 1013, Kaido defeats Luffy for the 2nd time and as he’s falling off Onigashima, Kaido says “Looks like you couldn’t be Joy Boy either.”
This implies to me that Kaido thought someone else was Joy Boy before, but that hope was dismissed. I also believe Kaido thought that Joy Boy was himself.
In Chapter 1035, when Kaido saves King (who is very handsome), he tells King that ONLY HE (Kaido) can change the world. I don’t think that was overconfidence. Kaido really seemed to think he was Joy Boy or that he could be Joy Boy.
But some event after that proved to him that he wasn’t Joy Boy. Or better yet, maybe some event proved to him that Oni people can’t be JoyBoy or he misinterpreted something like that. I believe this is one of the reasons why Kaido says “These people won’t accept you” to Yamato. Because maybe Kaido thinks he can’t be Joy Boy only because he is an Oni.
I think ever since Kaido knew that he couldn’t be Joy Boy, he began to search for someone who can actually be Joy Boy.
In Chapter 972, Oden tells Wano that 20 years later Joy Boy would come to Wano, but Kaido didn’t react to that at all. Almost like he already knew this.
I believe Kaido is in Wano to see who Joy Boy actually is. To see what Joy boy has that he doesn’t. To see why this person can be Joy Boy, but he couldn’t. So he invaded the one place he knew Joy Boy would definitely come. Wano.
In the Marineford Arc, we know that Kaido was on his way to Marineford with King to fight Whitebeard. But what if it wasn’t to fight Whitebeard? What if it was to save Ace?
Ace came to Onigashima to fight Kaido but Kaido wasn’t there. So he fought Yamato and tied with her. He broke Kaido’s dragon statue as well. Maybe Kaido took this as a sign. Maybe Ace was Joy Boy. So he didn’t want Ace to die before he could fight him. But he never made it to Marineford because Shanks intercepted him.
I think Shanks convinced Kaido that Ace wasn’t Joy Boy. Which is why Kaido went away. This could add a new wrinkle to Shanks’ character as well.
2 years later, Kaido had grown tired of waiting. He has also heard of this now infamous “Worst Generation” of Pirates. Maybe Joy Boy is one of them. So when he received Intel from Apoo that Kid, Killer and Hawkins were there, he personally dropped in on them, to check whether Joy Boy was one of them.
Think about it. Why did Kaido go there personally? Why not send King and Queen? They could’ve handled it. He sent Jack (who has no named attacks) for something as important as taking back his most important business partner Doflamingo, but he went personally to capture a few Rookies? Why? I believe it was because he wanted to find Joy Boy. But he realized none of them had what it took.
When Big Mom told Kaido she wanted to kill Luffy, he objected. One of the main reasons I believe is because he wants to meet Luffy. He wants to see if Luffy was Joy Boy. And he is still interested in Luffy because out of all the people who have gone head to head with him 1v1, only Luffy was actively fighting for his friends and to free Wano. Not for clout, not for personal vengeance, but for freedom.
So overall, I think Kaido wanted to be Joy Boy but couldn’t. So he put himself in Joy Boy’s path to see why he couldn’t be Joy Boy and to maybe even die by his hands or because of him.
*Theory by OkUnderstanding3669