Riot please explain

How is it possible that I am one game away from my promo games to silver 1 and I get a team composed of 1 silver 2 player, a low silver 3 player and two unranked players. I understand how mmr and elo work, but both of these player couldn't not play and clearly didn't understand the amount of information needed to even survive outside of bronze. The both kept running with each other and both fed all game. The nasus had 60 stacks on his Q 16 min into the game and later refused to farm, while the talon constantly ran into 1 v 4 or even 1 v 5 and die. This does not make any sense to me and I would honestly like an explanation for why this just happened.