You have said that the Original Ones left towards the ending of previous cycles, as humanity seemed to lose their reason and integrity. What is the purpose of their staying amongst humanity this time? It is such a difficult challenge to observe the human fear, rage, and loss of reason.
When a civilization reaches its culmination, as societies on Earth have, there are two ways this could end. Either through pain and destruction (this way leaves the few survivors so traumatized and disempowered, that they descend into a primitive state of evolution) or through praise and gratitude pushing them into transcendence; into a higher reality.
Because the Original Ones have such a luminous, advanced consciousness, they are here to help create the second solution. The treadmill humanity has been on hasn't really allowed them to advance spiritually, since they keep having to start over again. The second way of preventing the fall of man is obviously much preferred.