Things moved fast, when war already seemed certain. The shaman found out of nowhere another tribe to bolster their ranks decimated by the epidemic, and used it to serve his narrative.
And even if we know he's right to be wary of colons, even if we can tell he's right to be thorough enough to get rid of not only the Nords but their things too, not everyone will see the bigger picture.
Self-interest. Greed. Opportunism. The same constant hindering any collective endeavour. Same issues his enemy Thornfinn had to deal with.
Hilde was somehow robbed twice of her chance to prevent the war with one shot. I don't see anything useful with this method now, so it's pretty dire when Thorfinn's utopic ways now have the only shot to entangle that mess.
I think he should use the little insight they got from the report on Markland. Helping the Lnu to quell and maybe stop the disease would be good to clear the slate.
... But once again, all it would take would be a simple guy pointing out that it did come from the Nords for fingers to be pointed at others again.
Welp. Better luck next time, Karli will go far! That's the only thing left at this point, hoping the next generation will take up the dream and carry it a little further. Thors made a warrior out of his son, who convinced even more people that kindness was the way.
It clearly isn't a total victory, but it comes with renouncing to see the world through violence. Success is much more subtle.