The efforts to stop cheating in Counter-Strike: Global Offensive, something the game is suffering from on a huge scale, culimnated in a policy change last month that saw the game requiring players to pay a $15 fee if they wanted to play in competitive games. Previously, players could compete their way in after a period of time, in addition to paying for access.
The change has seemingly lead to a nearly 17% drop in players (or around 100,000 players on average) since it came into effect, according to SteamCharts, and while some of this may be natural fluctuation, it's a fairly significant drop and larger than you'd typically see, being the biggest fall-off since 2018.
This may not be a bad thing, though. It suggests that the change may in fact be doing what it was intended, and Valve has stated recently that since the game went free-to-play, it's suffered a lot of "bad actors" trying to "hurt the experience." The company is hoping the new paywall will keep cheats and bots out of the competitive modes.
The game is still one of the most popular on Steam, too, the drop off is big, but not too dramatic, for the game. In an added bonus, bot accounts that farm for Prime status to be sold on have little reason to exist, which may lead to a reduction in bots generally across all modes.