Board Game Arena

I came in first for a game that someone left after 85% played but I beat the other player yet they got 16 points and I got -2 what is that about.
I just came in second and got -2 and te winner got 26 points, how does that work.

One reason to include expansions, is that there are many more top tier cards, which makes it more likely that all players will have access to one or some top tier cards.