I think it was a mistake for Luffy to fight Kaido this early tbh. Now Oda has to justify all sorts of garbage not to let things get out of hand.

Dude kills the strongest Yonko and erases him from the planet, but his bounty is lower? Tf? Which of the Yonko have managed to kill and depose another Yonko?
perhaps bounties are also based on territories
and influence held overtime
like you rack up more as time passes on .