Help with matches ending prematurely?

I am a relatively new player, and I don’t quite understand why some matches end with ships on both sides and plenty of time left. I mainly play co-op, even though I’m not a fan of how easy it is (just like to relax).

I thought it had to do with the bases and “points,” but now I’m seeing a lot of matches where bases have already been decided for a while and the match will just end.