Re: What happened to the Romulan Empire after Romulus was destroyed
Star Trek makes mention of several advanced, supposedly interstellar civilizations ceasing to be when their homestar goes supernova. Probably not overnight, but still. Supposedly, then, the evacuation of a couple of Romulan bigwigs to another planet in the Star Empire, and the establishing of a new government, would merely slightly delay the inevitable: by some unknown mechanism, the conquest and dissolution of the Star Empire by its enemies would be assured.
The main one being perhaps the T'Kon Empire, that collapsed when it's central start went nova.
And it had a population numbering in the trillions.
As others have said, could conquered/occupied worlds rebel against their oppressors?
On the continent of wild endeavour in the mountains of solace and solitude there stood the citadel of the time lords, the oldest and most mighty race in the universe looking down on the galaxies below sworn never to interfere only to watch.