What if the reason Whitebeard ‘did not help’ Oden with Kaido was because he was stopped by Big Mom?
And that was the life long debt that Kaido owes Big Mom?
Whitebeard tried to go to Wano and assist Oden but Big Mom intercepted him. By doing this, Big Mom ensured that Kaido owes her a favor.
25 years ago: Oden went back to Wano, confronted Kaido and Orochi. He backed down and started dancing every week.
24 years ago: Roger got executed
23 years ago: Moria and Kaido fought in Ringo region of Wano
20 years ago: Oden got executed.
I believe at some point between 20-25 years ago, Whitebeard caught wind of what happened in Wano (either through Izo or other means), wanted to help but was intercepted by Big Mom.
I strongly believe Whitebeard was stronger than Big Mom but I seriously doubt even the Whitebeard Pirates could take on 2 near yonko/yonko level crews back to back.
The next time Whitebeard heard anything from Wano, Oden was already dead.
*by battlehunger96