Undoubtedly, based on the situation at the time, if they were not fully prepared, they would be absolutely powerless to resist Zhou Tian's retaliation. Thus, to ensure their safety and benefit, those Ancient Powerful Beings hurried back to set up defenses after learning that Zhou Tian had left.
Although those Ancient Powerful Beings knew very well that even if they set up defenses, it would still be very difficult to stop Zhou Tian. But, even just for peace of mind, they could not possibly stop their actions at the time.
After all, if they could set up some defenses, they weren't expecting to really stop Zhou Tian, but with those preparations, their hope of survival would certainly be much greater. And if they did nothing, given Zhou Tian's strength, once he found them, those Ancient Powerful Beings feared they would have no chance of survival.
