It will be discarded in the worst possible way, an opponent who doesn't add anything to the story.
- Kaido and Big Mom had territories
- Military power and treasures
- Road (of paramount importance to Luffy)
- Kaido dominated a crucial point for the coming of Joyboy and any other subplot that Wano still holds for future events; having one of Luffy's allies ruling this location is beneficial for him.
Kizaru:
- I have nothing to offer.
- I don't contribute anything to Luffy's pirate career.
- My objective is to be kicked, and that's it, to validate that Luffy or Zoro are capable of defeating an admiral at this point.
The big player here is Saturn, who is more important than Kizaru and certainly adds more to Luffy; for example, Saturn can be used as a bargaining chip, can say things that only he knows, imagine the Revolutionaries with Saturn captured.
Kizaru is just a Hody. Lmao