I'm gonna go on the record OOC here and say again that this is factually FALSE. The crusade was, in point of actual, material, real facts, NOT motivated by "political" reasons such as Hireshmont's desire for personal power or bitterness at Triunists for seceding. In fact, I think a really political war would have been much easier to get people to support.
But it obviously wasn't done in the church's best interests, the current state of the church attests to that. If Hireshmont was sincere, then he was short-sighted. He should have listened to the voice of reason and not brought the North into a crusade to save an undeserving city-state.