So do y'all think something along the lines of napolean couldn't have happened in medieval times? Aurvandil even kind of follows suit with their break away from Madina and the hardships they've had to deal with. Therefore, I think it would be perfectly logical that the people of Aurvandil could come to believe only in their monarch.
Logical "what if's" are always dangerous. Given time people could construct a what if that would give rise to a modern democracy in a medieval setting as well. I could however easily see a realm elevating their Monarch in such a way, but then I would also see them building temples and rites around it. If you are going to transfer the relevance and belief in deities to a physical being, to me it would make sense that you basically elevate them to the position of demi-god.
That said I see no reason why there is a problem with Aurvandil as is. Obviously the peasants are happy to follow numerous and varied local pagan systems. Without large organised religions operating in the realm and converting the peasants I see little reason why a nobles religious beliefs would not be a private matter.
