That was Pangaea. Arco ran out of provinces while trying to take it back. And Van had help taking out those last provinces. Maybe your scouting net isn't quite as good as you think
So I think the point goes to Pan.
I didn't think this changes even if Van takes arcos capital now. Only Arco could have taken it back enabling someone else to claim the point? I thought that was the whole point of the scoring. Otherwise you can simply play in cautious/turtling sort of way and as long as your end game is good win by taking over a large portion of the world.