yea especially they seemed to be sentient enough to be able to wage infiltration war with Ishgard, so I would think their aggression has something to do with them summoning/waking/losing their king and I would think its the Ishgard that did it, they made Midgarsomr fight the Empire and had promised support but they didn't support so that was what caused war between them. because from what I understand there were hostilities before the Empire's advance into Ala Mihgo but there wasn't open war, the open war only started after the Silvertear.
