Over the ages of Anu living on Earth and working with humans, much of their technology had made it down to the planet. Advanced technology was used for mining and building, for coordination between temples, to improve both armies and individual soldiers. The Me were used to teach humans and develop their culture.
After the scientists had been cast out to the surface, the remaining Anu began to remove all of their technology from Earth. They could not risk the others getting their hands on flying craft, long distance communications equipment, or weapons.
This was the end of the very advanced civilisations on Earth and the end of the time where the Anu Gods actively helped humanity to develop.