Well, the rules of inheritance aren't strict, and that was part of the consternation. But Sileon is nowhere near the one that Aroesus favored to inherit should something happen. Neither would Aroesus' eldest. It's more fluid than that and has to do with favor and the like.
But Sileon isn't awake, and certainly isn't releasing people from Sharzunates. Sharzunates' defenses weakened considerably at the moment of Aroesus' death, and the power to hold deities there was weakened considerably. Those deities may not be able to just walk off, but they can certainly be rescued easily enough now.
The whole point of this RP will be the future of the pantheon -- will the Pantheon even continue or will a new order arise? And then, the consequences of the strife on the world and so forth. Aroesus might have an heir picked, but they won't get to just walk in and take over. This is a contested succession.