Comment by sushibowl

You are absolutely correct. Valve's linux push was driven by developments in the windows platform, specifically around the release of windows 8. Microsoft was pushing a windows store similar to Apple's app store, and Valve was unequivocally stating that they were worried Microsoft would basically lock down the platform and only allow software sales through their own store, destroying their steam business. Gabe said it plainly himself (https://www.bbc.com/news/technology-18996377):

> Mr Newell, who worked for Microsoft for 13 years on Windows, said his company had embraced the open-source software Linux as a "hedging strategy" designed to offset some of the damage Windows 8 was likely to do.

> "There's a strong temptation to close the platform," he said, "because they look at what they can accomplish when they limit the competitors' access to the platform, and they say, 'That's really exciting.'"

> This is seen by commentators, external to be a reference to the inclusion of a Windows Store in the Microsoft operating system.

Having an open platform is good for consumers, but Valve is primarily looking out for themselves here. Gabe realized that windows could take Apple's IOS route (i.e. https://blog.codinghorror.com/serving-at-the-pleasure-of-the...) and lock down their OS, and everything he's done since has been an effort to protect his company against that existential threat.