Most likely those people are not smurfing.
There is something about this game that makes 1 person play very well in each mach. I have proven this, but using tracker to check the people I'm playing against. You can do the same.
Keep in mind, I'm only in Silver, and I've been stuck in Silver for the past 12 months (solo Q). But I realised that every game I play.. one person is on an abnormal amount of kills as compared to everyone else... so those people going 35 or 40k. Everyone else is down on 20 or below, including people on that person's team.
For a long time I was thinking.. this game is full of smurfs. A smurf in every game?? So I got smart and decided to check tracker and see what sort of numbers these people put up in other games. It's always the same story.... The person who is on 40 kills and destroys me everytime I see them, has just an average and many times bad K/D record in EVERY other game in their history. If you look at their history they give the view they are a terrible player, but this one game they are on 35/12.
So I dug deeper.. and I realised this happens to me. I will have average results for a while.. so usually somewhere between 10 - 20 kills per game, but I usually struggle to get over 20. But then I will have 1 game every now and then where my aim and hit detection feels insane. I'll be the 35 kill person, and people accusing me of being a smurf.
In conlusion... these people are not smurfing. The game either applies and RNG to one person every match, so that person can much more easily hit headshots and has huge hitboxes, OR there is some way the server is favoring 1 person above all others in terms of their connection TO the server. Ever get shot by someone and it feels like a 1 tap, but you see that you have been hit 3 body and 2 leg? But it's all over so fast, you hit the other person for 0? Yep.. this is what I'm talking about. THere is something suspicious about this game and the way duels play out. I've been onto this for a while now and I can tell you with 100% confidence that probably 90% of the 'smurfs' you refer to are not smurfs... just the server advantage or the RNG is on their side in that match.