so this took place around 24 years ago.. and Oden was killed 20 years ago. Could Oden took Wano back from Kaido before Kaido seek revenge 4 years later?
That is most like the most possibly way. Look at Hiyori, she was older in the flashback when she give Momo a dropkick. I think Oden take wano away from Orochi again and 4 years later after Orochi did something(poisoned?) Kaido and his crew invade Wano.
It took one whole year even without Oden to take control of Wano. I doubt Kaido would easily take control over Wano without Orochi help. This new timeline just confirmed it, he waiting for whole four years until he shows up with even show that Kaido show some respect against the Wano millitary force(Can understand Akainu here).
Wano isn't like countries as Dressrosa,Alabasta and co where the villians easily take control on the land, after all Wano has himself a Top Tier(Oden) and some strong High Tiers with also large number of soldiers. Even for a Yonkou it would be risky to attack a land as Wano without any plan, a all out war would cost in both side so much lifes. Their is a reason why Kaido working up together with Orochi and wait 4 years until he could move.
I don't like the idea of Orochi poisoned Oden, but with each new chapter I think this was the way how Oden was easily take out later...