The magical thing is that they've done so much work with Proton that a device like the Steam Deck is more than a curiosity. It is a viable product. It is viable to play games on Linux in a way it has never been before. Even better, they aren't keeping it to themselves.
A purist ideology about linux isn't going to change reality. But Proton is. The Deck is a wildly popular device and the knock-on effect is going to be more systems running linux for regular people. The games may not be native but if they're indistinguishable from native games, then who cares? Meanwhile adoption of linux as a viable platform still goes up. Maybe on a long enough timeline things swing around, though I still very much doubt that.
The Year of Linux on the Desktop is still a fantasy, but reading the steam hardware survey, it is more true than it has ever been before, thanks to the Deck and Proton.
1. Make wine really really good.
2. Start adding Linux-only features.
hehehe
If Valve gets gaming studios to target proton and guarantee compatibility, is a win.
If that's equivalent to gaming studios explicitly targeting MAME and QAing it, I'll take it.
Anyway it hardly matches Switch sales, for which studios do actually bother to actively support.