Benefit is the real reason those ancient powerful beings formed an alliance, because Zhou Tian's emergence and his actions threatened the core interests of those ancient powerful beings. Thus, at that time, those ancient forces with little previous interaction allied. Otherwise, given the nature of those ancient powerful beings, who aside from themselves looked down upon all other living beings and seldom regarded beings of their own level highly, how could such self-sufficient and non-contentious existences possibly come forth to fight Zhou Tian without reason?
Now, due to Zhou Tian's actions, those ancient forces found their interests in conflict. Even if the alliance wouldn't split because of this, there would certainly be some disagreement at that time.
