Why riot should be more focused on trolls then toxicity

I played a game where I had a Caitlyn and a Tristana on my team. Now the Caitlyn was super toxic but I didn’t care simply because she was good and knew how to play properly. Meanwhile my tristana was running in alone, refusing to group, and constantly trolling my team. The sad thing is riot will ban Caitlyn, who is the good player, over Tristana, the actual troll here.