Caerwyn has had their opinion of SA way before SA took /any/ sort of hostile action against anyone.
Back when Springdale(realm) was bigger than Morek and Astrum was small and Everguard was still around I sent emissaries to Caerwyn. I gave them lots of free food and tried to interact with them. I wanted to put a VE shrine in Donhaiwei and an SA shrine in Golden Farrow. Allison was snubbed.
That is the root cause of the Caerwyn/SA conflict. They ignored Allison and she did everything she could to make people hate them. From bribing a lord to build a temple which you then made SA take down. To seceding so it looked like SA civil war to goad you into attacking Astrum. (That last one wasn't really intentional just a nice by product)
All because Caerwyn took Allisons 2000 bushels of food and then turned up their noses.