Valve is truly one of the last respected game companies. Sure, they make a lot of money and take a 30% cut from developers on Steam, but because of how satisfied their users are, they keep coming back and keep buying more games, which is a win in the long term. Too many companies think short-term or quarterly while Valve seems to look at the big picture. I give a lot of credit to Gabe for not truly selling out at any point. And if it hasn't happened by this point, I don't see it happening in the future. It would have happened by now if so.

Its just sensible. Building their own os would take so much resources that they would have to successfully make a profit on it. Leveraging linux and the open source community allows them to make sure there is an alternative and gives them an os to use on their handheld device or any other they choose to make ensuring they can't be cut out by a monopoly power. And all for pennies really.

I have some vague memory that they started seriously pushing for linux support after microsoft tried to limite steam acces on windows 8 or something like that.
But I can't find any info on that...