Oden asked "Where is my ship? What bout Kaidou?"
-> obvious deal!
- Oden making a fool of himself -> people of Wano start to accept Orochi
- Therefore neither Orochi nor Kaidou will touch his family and friends
- And once the people fully accept Orochi as Shogun Orochi will give Oden a boat and Kaidou will leave the country
for 5 years Odens family and friends stayed untouched. Then Orochi came to Kuri making demands end up breaking the whole deal.
Why did Oden follow the deal? Oden don't care about how others think about him which was shown during flashback with Mountaingod accident or saving Hiyori. And he most likely thought Orochi only wanted to become the accepted ruler.
With the obvious deal we also don't need a continuation of the flashback, because we know what will happen. Oden and the Scabbards loose with Oden end up getting executed in the public. Denjirou, Ashura, Dogstorm and Cat Viper trying to stop forces while the others try to save Odens family. Hiyori dies, Kawamatsu takes care of Hiyori and the rest get send to the future together with Momo. Dogstorm and Cat Viper return to Zou, Ashura, Denjirou and Kawamatsu keep staying in Wano.