Most non-playable factions don't expand. The main exception in TR is the Yevethans who become hostile during the Black Fleet Crisis, which I believe is Era 5-ish on the progressive maps. If you also play Fall of the Republic, the other EAWX mod, the non-playable CIS companies expand but generally don't attack each other or the playable Confederacy faction.

What's strange to me is even though there are examples of aggressive non-playable factions, not a single playable faction defaults to passive when not controlled by the player. Given how lore-accurate the rest of the mod tries to be, I would appreciate a neutral Hutts / Hapans / CSA when not playing as them myself.

It's a game first. Those factions have a more defensively-oriented AI but if they just flat out didn't attack then they're just territory which would be ignored most of the time, and that's a huge chunk of the territory (which is determined in each map by trying to make as many viable factions as possible)

Originally posted by Burgundyne:

Most non-playable factions don't expand. The main exception in TR is the Yevethans who become hostile during the Black Fleet Crisis, which I believe is Era 5-ish on the progressive maps.

My personal experiance with the yevethans has been that they are only aggressive against the player. Though I can not say if that is because the AI bordering them actually has a permanent fleet presence the yevethan AI is not confident in beating or if it is coded to only attack the player.