As someone who's played CoD for at least 17 years now, when the hell does a CoD game ever have more players by this time of the game's lifespan? The only one that ever achieved this was probably MW2019, which pretty much was on life support until Warzone came out, a free-to-play offering during COVID which was also very GaaS-focused.
Black Ops 6 is actually great and a lot of fun though, the fact that its actually kept this many players is impressive for PC CoD, as usually it tends to die out around this time and get much more scarce (I remember Infinite Warfare had sub-1,000 players at one point in its active lifecycle on Steam).