Matchmaking error?

I almost tasted gold for the first time this season, my climb through silver was the smoothest it had ever been. But then I lost my placements because for each of the games I had at least one, most of the time, multiple people inting, trolling or straight up going afk.

Something clearly went wrong, because the people I was getting matched up with during and after my placements were pretty much the opposite of the people I had the pleasure of climbing with. No one speaks proper English, everyone is constantly screaming REPORT over every little thing, threatening to outright int or afk over any small inconvenience to them or just doing it anyway, there's no coordination or teamwork because everyone refuses to cooperate in any way whatsoever.

Just as an example, last game I had a Wukong try to gank a level 6 Cho'gath, at level 5 with half health in the middle of a full minion wave. He of course got eaten instantly then decided to ? me about 15 times before going back to farm. He tried again when he hit level 6, but Cho'gath was level 9 at this point and Wukong had no mana to do anything and he of course got eaten again so he takes it to the next level and starts flaming me and running it down top lane, giving Cho as many kills as he could before he got bored and moved on to running it down the other lanes, which causes the rest of them to start blaming me for Wukong's stupidity (which wasn't his first time doing something like this, I checked his history and he has other games where he fed his brains out and had 6 faerie charms).

The game before that I had a Shyvana jungle who got invaded not once, but twice, by the enemy bot laners and instead of going topside jungle to avoid being killed again, she decided to run it down bot because they were to blame in her mind and everyone had to suffer for it.

Games like this have been consistently happening to me as I plummeted right back down to S4 where I struggle to maintain the rank because of these people and I can't help but feel as though I was mistakenly dropped in EU servers or something, and I don't really know what I'm supposed to do about this.