From the inexplicable message from the exploration fleet of a millennium ago to the defeat and capture in the interstellar war, and then to entering this satellite prison, all the oddities that baffled them were explained in an instant.
There are numerous civilizations in the universe, each emerging from different environments for survival and evolution, so it's not uncommon to encounter civilizations with high moral standing.
Some powerful civilizations possess extremely advanced technology and never worry about precious energy resources. They don't need to expand outward to amass rare elements, instead preferring to maintain order in a region over aggressive conquests and slaughter made possible by technological superiority.
The civilization they faced this time might meet the mark technologically, but morally, it was another oddity.
