Questioning the Matchmaking system, need genuine help to understand.

So it happened a few time this season, and I just can't figure out what's wrong. Here's an example, yesterday I was on roll, climbed a whole rank and a half without a single loss. And then the trolls start appearing every single game for about 5 to 10 games, insanely toxic people, unranked players that obviously aren't smurfs and so on. What's happening here ? If it happened to me like once I guess I could simply blame bad luck, but it seems pretty consistent. Go on 10 wins in a row and then endure what I stated above and the cycle starts again. I'd like to read opinions or genuine knowledge about that. No ''RiOt DoEsn't CaRe'' Although the system is clearly not perfect, I'm pretty sure they try to have a healthy matchmaking system.
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