Only living beings making those arrangements at the time could hardly imagine how much more potent Zhou Tian's ability to conceal himself was than they had anticipated. In an area they thought it impossible for Zhou Tian to hide, there he was, hiding right under their noses.
Just as the opposing team split their forces, Zhou Tian not only regained the advantage in strength but already had the ability to annihilate the remaining living beings. Even when they believed that Zhou Tian couldn't possibly be in that area, Zhou Tian still had the opportunity to launch a surprise attack on them.
In fact, Zhou Tian certainly wouldn't miss such an opportunity.
After waiting a long time for such a moment when the enemy was scattered, and they had even given him a chance to attack by stealth, if Zhou Tian didn't fully utilize his current conditions to land a severe blow to the other side, he would feel he was doing a disservice to the opportunity at hand.