The matchmaking system in CSGO almost makes a conscious effort to increase "smurfing". Back in 2013-2015, smurfing was actually a lot harder, because if you won every game, your rank would increase very quickly. This led to a situation where the rank distribution didn't look anything like a bell curve, because people with higher rank had proportionally many more accounts than people in lower ranks.
For some reason, Valve thought that this was a problem. And they modified the matchmaking system in a way that forces the MMR distribution to be a bell curve from the outside. It's not known what exactly they do, but from tracking sites it seems like the distribution starts to "deform" over the course of a week and then gets "squished down" again.
As a player, the effect this has is that 1. accounts at the upper ranks (Global Elite/SMFC) decay really hard, like if you have an account that is GE and you don't play on that account for 3-6 months, you'll be like MGE afterwards. My main account got actually re-ranked from GE to MG2 after they shifted the ranked distribution - after which I won, and this is not an exaggeration, 38 games in a row, and still kept like 75% win rate until the account was GE again. The other effect is that it takes way too long to rank up now, it used to be that if you won 6 games in a row you would very likely rank up, now it can take easily double that.
Put those two together, and you've got a million smurfs obviously. Because anyone who just bought 10 accs for $70 during a sale (and believe me, many, many people did that) can just rotate around accounts and let them decay again once they're too high to smurf on.
Add to that that there is nothing to do once you're GE, there is simply no higher rank, and yeah it's no surprise the game is full of smurfs.
To make things worse, now that Trust Factor exists you can't even compare experiences anymore. If a new player comes to me and says oh I only play against cheaters or smurfs, I can't even give him a way for it to get better. We have no idea how Trust Factor works, and if you're a new player with a bad Trust Factor... what are you gonna do? You have nothing to look forward to. Prime barely even means anything anymore (not that it ever did, but at least it was a small hurdle), and there's no given way for you to increase your Trust Factor.