My brother and I were playing a 6 player LAN game, against 4 'normal' computers - we just got the game, and had played an experimental 1v1; this was our first real game.

In any case, after about 4 hours, we had eliminated two of the computers and the fleets of the other two, and were moving through their planets. I had decided to clense the pirate threat once and for all (they were annoying, and nobody else had any sort of fleet to speak of). I jumped my entire fleet there, and after about 30 seconds 'clensed the planet of heathens.'

For some reason, the Victory sceen then popped up. We had not eliminated two of the computer players, though one of them was reduced to only one planet and neither had fleets. The pirates had just been completely destroyed, but that shouldn't have mattered. Our combined culture had spread throughout 98% of the Star System, according to the post game statistics. Could this have mattered?

Are there any conditions for victory other than military domination?