It's just "smurfing" and fairly common in unrated on most games.
General musings on the decline of online gaming

Increasingly common, and thoroughly low class. "Smurfing" is the cutesy term for what in the real world is known as being a d-----bag. It's a lowlife stunt played by low value losers in life, but socially maladapted people get away with it because they have a computer screen to save them from having teeth knocked out. IRL they get dealt with, harshly.
*edit: congrats on England's WC performance to date BTW, the side looks good.
A regular topic in the General Chess Discussion forum is whatever complaint aired over what chess.com does or doesn't do, or how moderators need to do this or that, or why the site is subpar, or whatever the gripe of the day might be. But from my perspective chess.com is fair and does a very good job overall. Mods and tech staff alike have always been courteous, kind, and very helpful both to me and to players I know, personally. They are very consistent.
So why then so much discontent?
My take is that online gaming is a reflection of the world population at large, and the english-speaking world in particular. And, by Q4 of 2022, people in general have become pretty bad: narcissistic, arrogant, self-centered, and immoral. These behaviors have, today, run amok in online gaming, just as they are rampant everywhere else in the world we look.
As just one example, here, a year or so ago, playing as a Guest/Beginner level was a good way for the inexperienced player to experiment with openings and tactics which, if they failed, had no consequence. Today, it is nearly unusable. Guest/beginner is choked with high skill players beating up on low skill players for whatever reason - perhaps they get a good laugh out of it, or feel better about themselves somehow, or it makes for a good stream - but it has reduced the Guest section of the platform to a virtual sewer of bad behavior and bad sportsmanship. Real beginners are now few and far between in Guest/beginner.
In my own experience, I routinely run up against players in the 1400-1600 range there - often playing bullet-style with a 10-minute time control - and when I do, I either abort the game or more commonly just resign so I can move on. I have no desire to play losing contest after losing contest against someone twice or more of my own, low skill and lowly rating.
But conceding defeat doesn't end the misbehavior. The same player will smash the rematch button over, and over, and over again after I resign, again and again ad nauseum. It suggests to me that many people online today are simply sick in the head.
Anyway, there's nothing to be done about any of it. It will go on and on until world events tear people down low, and make them humble, again. But I do think it's important to recognize that chess.com has nothing to do with it, and that I don't think anyone does a better job of ensuring fairness and fair play than chess.com, does. But in today's world, even the best sites will struggle with the planet's growing population of miscreants and their cretin behavior.
That is all I have to say. Thanks for letting me vent. 🙂