Although he was in the midst of their team, in essence, that organization was naturally Zhou Tian's enemy. As his enemies, Zhou Tian naturally wouldn't mind finding ways to reduce their strength.
After all, from Zhou Tian's perspective, that organization was a volatile entity. Even if his own forces developed well in the future and were several times stronger than they were now, based on his understanding of the organization, if there was ever a conflict or if they simply launched an action, Zhou Tian could face total devastation.
Therefore, Zhou Tian stayed in their lair, firstly to enhance his own strength, and secondly to find ways to weaken their strength as well. After all, given the vast distance between Zhou Tian and that deity, the organization was a bigger threat to him at this point.
