Because religion may be an undertone of the war but it is not the reason. It's only one of the frustrations.
It could definitely have gone the way of holy war, and Maya was champing at the bit to go that route, but the 'war of catharsis' is just as good a reason from a noble perspective. But poor poor peasants who must die by en masse for our designs.
The Battle of Lastfell was pretty epic. Though it was a defeat for Melhed, we did do some damage and wound the Thal king!