For a long time, there have been representatives of other non-terrestrial intelligent species observing the Earth. While they were not yet here when the Anu first arrived, they were aware of the Anu’s influence and the resulting suffering later on.
They did not interfere. The races outside this world are part of a great bureaucratic system, that holds as one of its tenets that no one is allowed to intervene with the development of pre-sentient species. In the past, this has led to great horrors. They have only helped – discretely - in a few select cases.
At the moment, because of our savagery and tendency to violence, Earth is isolated and marked as quarantined.