The scabards are legends, they do know they dont have a chance against kaido , but they also know the profecy they have to Carry, and its NOW, not later. Theres no more time to plan a way to take out Kaido with some weapon or other existhing thing , has to be now, as toki Said,* 20 years later*.
and they Go, and their faith IS on their aliance to be the miracle they need to fullfil toki profecy.
they Did a Lot with the little time they had, found the rest of the scabards, found great captains to fight at their side, has thousands of samurais as their side. They lit the flame toki wanted, and their effort Will make wano great again.