Their 'future' is already the past, and when they go to the 'past' it became their present, so the future they know already changed by their present.. so it's already unpredictable (only known by the author)
They just trying to survive that's all, even if they not choosing sides at the start they will eventually and maybe worse than now if MC not offer her skills into Oda faction.
And considering there are multiple person got time travelled it's bound to have one person that have knowledge about killing wpn, (don't we all too?? even though its superficial knowledge but at least we know the theory or how they works, and some talented person can make it happen like the blacksmith dude that i seems to forget the name)