This was also a last resort. Once the Soul World was closed, it meant that there would be no new souls born into the Three Realms. There would be no newborns. The Reincarnation Oath would be completely sealed and completely isolated from the Three Realms.
This decision of the Spirit Tree was no longer related to just the Soul World, but the whole of the Three Realms!
However, Jun Wu Xie was clear that the decision of the Spirit Tree was wise. The Upper Realm could sneak into the Spirit World once, they could sneak in a second time. After finding out the situation of the Soul World, even if there was no betrayal like what Meng Qiu did, they would have done whatever they could to achieve their goals!