The angels believe that as long as they can corrupt each world to the extent that the Abyssal World can annex it, they will undoubtedly achieve great feats. Although Zhou Tian did not explicitly promise them any rewards, judging by past circumstances, receiving a reward of a Sky City could mean a strengthening of several folds in their power, which seems entirely possible!
With this in mind, even without Zhou Tian's direct involvement, those angels independently initiated corresponding actions at that time.
Intentionally or unintentionally, Zhou Tian left some different world space coordinates in the minds of those angels. Given their abilities, they naturally did not need Zhou Tian's help to enter those worlds. Thus, after Zhou Tian offered rewards and secretly prompted the emergence of those changes, those angels quickly grouped in threes and fours and embarked toward the lower realm.
