The goblins did just as they had planned. As soon as they found out that the NPCs had retreated because they couldn't battle Zhou Tian, the goblins didn't hesitate and took action right away. It didn't matter if they had the power to handle Zhou Tian; as soon as he scored his victory, they immediately sent out troops and frantically seized the spoils of war.
It was intentional by the NPCs, when Zhou Tian forced them to retreat, and with the goblins' inability to claim much territory due to the resistance of the NPCs, the goblins effortlessly took over most of the NPC lands.
Although the goblin's strategy had flaws, based on the existing situation, they had the advantage. After quickly annexing the NPC territory, if those goblins managed to drain those lands, the territories they owned could potentially upgrade their previous Pope Level power to a King Level one.