I feel that this flashback is setting up kuma to end up sacrificing himself to take out saturn and allowing the strawhats to escape which i think will be the "big incident" that we are told will happen on egghead.
Would still make the Straw Hats frauds though, and Elbaf will be Wano 2 in terms of length. God I hope the Straw Hats repel the Marines somehow. Story needs to pick the pace back up if we dont want Egghead to overstay its welcome.