Big spoilers for pretty much the entire HW storyline
So, why exactly did King Thordan and his knights decide to murder and eat one of their allies in a way that was guaranteed to sunder their existing civilisation? Comparing Isghard to the ruins of Avalonia and Zenith, it does seem like their culture took a definite downgrade in the aftermath.
Were they just weirdly racist for a bunch of guys raised next to dragons their whole lives and also wildly optimistic about how the plan was going to go? Were they just assuming that all the other Elezen in the kingdom would be cool with it? Were all the other Elezen in the kingdom cool with it?
Like Hydaelyn herself, I'm very confused as to the whole chain of events.