Head to SteamDB and you’ll see the peak player count the pirate game posted around the time of Sea of Thieves’ Steam release in June last year hit a whopping 66,906 (on June 18, a couple of weeks following its launch). Similarly, Steam Charts puts the peak concurrent player count for June 2020 at 66,632. Numbers stayed high for a goodly chunk of July, too, with Sea of Thieves selling a million copies on Steam and having its biggest month ever overall – at that time – as of July 20. However, peak numbers hit each month following this have drifted down to figures somewhere between the 13.2k and 29.2k, according to Steam Charts’ figures.
Now, though, both sites’ records show that for December 2020 Sea of Thieves’ peak concurrents shot up to over 45k, which was hit at the tail-end of December, and its risen further since. Plus, it looks like – as stats tracker site PlayTracker notes – it looks like the Steam Winter Sale is behind the enormous climb.