I think its some massive hefty ass plot armor that Oden was friends with 2 of the yonko and that neither of them wanted to kill kaido.
Like just imagine if 4 years ago when shanks became an emperor, he decided to team up with WB and go on a covert mission to kill kaido. No giant fleets or anything, just maybe a small going merry sized boat containing WB, Shanks, Beckman, Yasopp, Roo, Marco, Jozu, Vista, and teach.
Like what the fuck could kaido actually do? And imagine if they invaded onigashima on any other day apart from the one day when all of kaido's forces were on that island.
Like just imagine if 4 years ago when shanks became an emperor, he decided to team up with WB and go on a covert mission to kill kaido. No giant fleets or anything, just maybe a small going merry sized boat containing WB, Shanks, Beckman, Yasopp, Roo, Marco, Jozu, Vista, and teach.
Like what the fuck could kaido actually do? And imagine if they invaded onigashima on any other day apart from the one day when all of kaido's forces were on that island.