The Centauri Republic tended to go after species where they could get
some advantage; they'd find a world on the fringe of being able to hit
space, with a technological base, move in and take over. It's sharper
and easier than taking over a world without tech; not much to offer. By
the time we got to that point, they had begun the decline of their
empire, and basically greeted us with a shrug. And there is no EA rule
about non-interference. The only real rule applies to surveying distant
worlds for mineral resources, and a restriction against strip-mining
worlds that contain sentient life.

jms