Well like you said when you started trying to win, you became toxic. I dont say toxic shit in chat because I realize that everyone has trolls and feeders sometimes. If you have trolls on your team, just tell yourself ok thats 1 troll game down. Just filling my quota. Eventually the other team will have the troll.
Also, it's not all about winning to me. If I win, that's great, makes me feel good to win. But no one wins all the time. You should have about a 50% win ratio, so when your allies get outplayed and look like newbs because of it, that makes perfect sense. Everyone on here is a human... humans outplay other humans. It happens. If this was PvE I could understand being upset that an ally still hasn't mastered beating an AI opponent... but this is human vs human. Just because they got outplayed, doesn't mean they are complete shit at the game.
I also heard of this 40/40/20 rule that helped put things in perspective. 40% of games you will stomp no matter what. 40% you will be stomped no matter what. And 20% of games your performance will actually influence the outcome of a match. If you play poorly, you'll contribute to losing 20% of the time, but if you play really good you'll win that game 20% of the time. So when your team is losing, just chalk it up to matchmaking doing its job, ensuring that you stay around a 50% win ratio. Don't get mad. Improve your own skills, the rank doesn't matter.