not really, while the sword did fan the flames it did not cause the initial spark.
Yeah, the original spark was fear. The Lnu, specifically the old shaman, were afraid of change destructive to their way of life, afraid of changes toward a different way of living for them.
That's why he consulted the spirits, the visions of which caused him to try and attack Thorfinn with an axe, which caused the hotheaded youngspawn viking to cut of the shamans hand.
Many things went wrong here, you could say it was fear, or conservatism, or the foolishness of youth, also the unpreparedness to lead on Thorfinn's side.