Matchmaking wtf-ery

Why was I just in game as someone who hasn't played ranked and with 2 silvers I didn't know on my team get put in a match against a Diamond 5? How did the matchmaking system come up with that idea? The effects of, what I assume to be a massive fuck up in the system, this were felt immediately as I got the shit stomped out of me laning top against him. How broke is matchmaking that me, not technically even bronze, gets thrown up against that kinda of player? How the fuck riot?