Speaking of civilizations that disappeared overnight without encountering war or any other disasters, everything seemed peaceful and stable, yet they vanished mysteriously. I always feel a sense of déjà vu... It seems like there are similar ancient city-states on Earth?
The entire city-state ruins were intact, and there were no traces of earthquakes or floods in the surrounding geological records, yet the people were gone, and history was suddenly interrupted. This kind of spine-chilling event seems like something I've heard of somewhere. However, what happened on this planet was apparently on a larger scale and more severe: it wasn't just one or two city-states that disappeared, but all the technological cities on the entire planet. And it wasn't some primitive civilization that had an interruption; it was a group of high-tech aliens who could already pilot spaceships beyond the Solar System!
