They aren't smurfs. Use tracker.gg and look at their histories. Most of them will have that ONE game where they fragged out.
There is something weird about this game that makes 1 or 2 people almost unstoppable every match. I used to think they were smurfing too. But after look at people's game history, I realized that it's not "popping off" for a match or a smurf. It's literally the game controlling who's "aim" is the best.