There was another use for the holy crystals. Yes, it could be used to build divine nations, sanctuaries for hosting the main body of the divine spirits to negate most enemy attacks. Even if the main body's location was found out, most enemies would have no way of breaking through the defense of the divine states.
There were a lot of advantages in holding one divine state. As the training ground for the divine spirit's main body, there tended to be better absorption for the worship power of the followers. Sometimes, the most devoted followers might just be drawn into becoming members of the state.