Provisionals makes no sense to me

So we started a 3v3 team, and we won 4 out of 5. Every single one of those games had at least one Platinum and one Gold on the enemy team. Two of the games had 1 Diamond on the enemy team. After winning these games, we only got Bronze 1. How does this make any sense? I did horrible in solo que 5v5 ranked and got Silver. Wtf.