Please rather check the payouts in the Victory progress panel, they are more accurate and show you the real ranking. You can open it by clicking on the upper left part in the resource bar that shows your current victory points.
Getting second place as solo player usually grants the same reward as each coalition member in the winning coalition gets, plus the VP amount. Reason is that winning in a coalition is much easier than doing it solo.
Sure, you could have split up and get a bit more gold for 1st and 2nd place, but 2nd place and 3rd place wouldn't have gotten +1 to their victory count and also no map winning achievement progress.
