Sins of a solar empire defeat?

how does defeat in any of the versions work?
i played SOSE for a long time and recently got entrenchment and diplomacy and they dont make sense
in one game in diplomacy there were 6 factions i had 60 and 100 relationship with two of them and was at war with the others, finally got a lot of the warfare research done and built a new armada to finish one of the enemis when i get a message saying “diplomatic defeat”
and today i was trying entrenchment there were 4 factions i was 100 ally with one of them. had already kille done of the enemies, took the pirate base and the last remaining enemy only had 3 planets left when i get the message “defeat”
how does that make sense?
Answer #1
No idea. I play with diplomatic victory off. Now lets google for it
Answer #2
this is a really good game lol