Reasons Why Wano Lost The War

Previously we were judging Oden's strength based on current nine red scabbard's Ashura Doji, Inuarashi and Nekomamushi who showed strength equivalent/similar to Jack thus placing Oden's strength around Yonko first/second mate or so and while having that kind of strength in Scabbards who were nine people and on top of that Oden and Hyogoro, they should not have lost the war, specially since only four scabbards could deal with Kaido's Top three who were a rather newly formed pirates however previous chapter revealed Ashura Doji, Nekomamushi and Inuarashi were much weaker twenty years ago and the fact that Kinemon was the leader of their group we thought maybe because he was good strategist but it is most likely that Kinemon was actually the strongest of them all nine Scabbards as well and if that were the case then Oden was also weaker than we thought, maybe around current Ashura Doji and so Wano the country of Samurai really did have weaker forces than we originally thought and the whole country losing to Kaido could be justified.

Here are the main reasons:

1- The Beasts Pirates had Kaido. Oden was strong, no doubt, but he's pretty much confirmed to be somewhere in between Roger/Whitebeard and Ashura Doji. If he was as strong as Katakuri, for example, it would already be more than enough to make him the strongest person in Wano, as Ashura Doji was considered the strongest criminal of Wano before being defeated by Oden. This is clearly not even close to enough to take down the WSC.

2- Kaido still had his own "Katakuri" (King) and other two powerful commanders (Queen and Jack), and a few strong "mid tiers" too (The Flying Six, or at least some of them, as X Drake obviously wasn't there, and possibly other strong headliners and allies). Even if they weren't as strong as they are now, they were surely pretty strong already.
3- Oden was backstabbed by Orochi. Not only he had to deal with one of the strongest pirate crews of all time, but also with internal enemies. Many samurai and ninjas, loyal to Orochi, certainly turned against him too.
4- The Red Scabbards didn't even fight, apparently. Orochi somehow captured Oden without notice and his retainers escaped (or were captured) after he was executed.