Yes, generating a Linux build wouldn’t require a lot of changes to the code.
But if they support Linux, they have to support Linux. This is not some student’s first indie game, but instead a massive game with up to 290 million monthly active users. That’s 3.7% of the whole world’s population! (And it’s also more than the number of total Linux users.)
So supporting Linux means they need to test on at least all currently maintained versions of maybe the top 20 or so distros on all sorts of hardware configurations. That would increase their testing costs by around a factor of 20.
They also need to support customers if they have problems. Considering the variability of Linux configurations, chances are high that this comparatively small segment of players will consume an aproportional amount of difficult support requests.
And lastly, if the Linux version of the game has some serious bugs on some setup, it might likely be that all these Linux users think the game is shit and start talking badly about it.
So it’s just a simple cost calculation: Does Linux support increase or decrease the total profit?
And if the variables change, the calculation changes with it. Exactly as Sweeny said in his post. People like Sweeny don’t care about ideals or about which OS they prefer. They only care about money.
And the revelation that a CEO likes money and dislikes risk isn’t exactly hard to figure out.