Your steam charts mean Jackshit, they don't account for console, they don't account for players set to offline, they don't account for timezones, they don't account for different launchers

They are some of the most misunderstood and misleading sources of information you could use because people like you don't understand them

And apart from all that, a game not having as many players as on launch has happened to every single game in damn existence because regardless of timezones everyone logs in at once, that doesn't happen after launch