I have a feeling it wasn't simply a utopia. You have to very different people together. Nidhogg though I have a feeling held a grudge towards mortals that predated the Elezen. I think he has issues that date back to the Allag. He tells Hraesvelgr that he told him not to trust the mortals.

The other thing I've been wondering on is Koji Fox said the lyrics of Dragonsong, the theme song, had potential double meanings much like Answers in what they refered to and Koji wrote them after he had seen what was planned for the story of the 3.X patch cycle. I'm wondering it perhaps Ratatoskr was attempting to maintain peace between the two races and Nidhogg manipulated things somewhat in hopes of triggering the war. He was the first on the scene.

That's not to say Thordan is innocent. Just that it was Nidhogg that set up the situation that allowed Thordan to do his thing.