Matchmaking Confusion

This game... I was baffled. I feel like I need to understand. I DO want to understand actually. But how does this matchup even happen?

https://i.gyazo.com/068d554452cf1420663f0343ee2180bf.png

This was a ranked game - in Silver. I'm not expecting to be playing with Unranked people. I expect to be playing with other Silver players and maybe low Gold and high Bronze players. I should NOT be playing with Unranked people. How does this even happen?

Long story short: Tristana could not handle Sona's passiveness as a support. As a result, Tristana went to various lanes expecting that the game was over. Zyra's compassionate heart took over for Tristana's place; however, she too became afflicted like Tristana. Zyra left the game, and Tristana allowed the enemy team to finish the game by sitting in fountain. As for Garen and Sona? - they were mostly mute the entire time. I could not believe the monstrosity taking place before my eyes as I tried everything in my control to somehow make an effort to win an impossible game.

Here's the thing: I am not angry. The game didn't even matter to me at this point (though it was a ranked, I was pretty upset). I'm just disappointed at how a matchmaking system designed to group players according to similar rank actually allows for an error this drastic for a RANKED game. 18LP was thrown out the window. And the worst part is I couldn't even do anything about it, but just try to no avail.

FYI: Queue time was less than 10 seconds if that information helps determine anything.