I don't understand how ranking works

I was viewing the ranks of some people in my team. There was one guy who was silver, and had really nice stats. Over 50% accuracy with the BR, about 80-90% games won. K/D was over 2.0 There was another guy in my team who was Onyx with 30% accuracy with the Assault Rifle, a negative K/D, and had only about 50% win rate. I played the game with them, and the guy with the silver did really well while the person with the Onyx went .5 K/D even though we won. Looks like you can get carried through ranks.