It was the best and most intensive game I've ever had in 2 years... not. I was premade with 
and 
but the queue time was like 2-3 minutes. Why do we get matched with high elo players?
So it's normals, and many people have a normals mmr somewhat different from their ranked mmr. I feel like higher ranks in particular tend to play almost exclusively ranked, so it's not that farfetched to think the master/diamond might have close to starting normals mmr (i.e. silver-ish). Those two are probably in a premade as well, so getting 'pulled down' by their silver friend. Also since it looks like you were queued with support as an option and still had a 2-3 minute queue, it seems matchmaking was having a really hard time finding a match (as support queue times are normally almost instant).
All those factors together probably lead to that game occuring, so that's probably the why. (This would suggest it's a very one off thing though, if it's been happening multiple times then something weird is happening.)
I'm also slightly jealous, as I've never had the chance to play with/against a master/challenger player. I've bumped into random diamonds and random rioters which is nifty, but getting the chance to really play against some of the best can be an insightful experience, as they'll basically punish every mistake you didn't even know you were making.
Conspiracy time! Riot got sick of hearing about ELO hell so they occasionally they shove high division players into low elo games to show them skill gaps.
