First and foremost, naturally, were those NPCs, because without the protection of the Divine Avatars, the NPCs had become the weakest faction. Although Zhou Tian's relationship with them was the worst, he knew that if he wanted to conquer other factions, the NPCs would undoubtedly be the easiest to subdue.
As such, one would pick the softest persimmon to squeeze first. When heading out, the first stop should be an easy target to deal with. And under these circumstances, those NPCs were consequently chosen by Zhou Tian.
Clearly, the departure of the Divine Avatars had the greatest impact on the NPCs. After all, whether fighting with Zhou Tian or covertly struggling against another Human Emperor faction, the NPCs depended on the support of the Divine Avatars. It was precisely because of the secret backing of these Divine Avatars that those NPCs, who were already lagging in strength, could still claim a place for themselves in the Main Plane.