This is just based on my personal experience, so please take it with a grain of salt.
Rather than gaining ground from the wider population, I see the recent rise in Linux usage as coming from a pool of “interested users” who have in one way or the other, had some prior exposure and thus interest in Linux. These people have already been interested in making the jump, but have been held back in one way or the other.
This shouldn’t be taken as discounting the recent advances amongst Linux distributions, however. Personally, the reason why I’ve made the jump is two-fold: dissatisfaction with Windows, and the advances in Linux itself that have made the jump far less intimidating than ever before. Not being a gamer, however, advances in Proton was only seen as a bonus, though a very welcome one.
Only one other person in my current friend group daily-drive Linux, and like me, they already have had experience with it beforehand. There are some other people I know of who have used Linux, but still, they all have had prior experience from school or work. For everyone else I know of, if they’ve even heard of Linux, they think of it as “for advanced users” and as one contact put it “way above my pay grade”. Unfortunately, in so far as personal experience goes, I don’t have confidence Linux will be shedding that image anytime soon.
As for the Steam Deck, I am guessing it’d be similar (with a lot of caveats) to how people see Android. It’d be seen as a separate thing, and not occupy the same mental space as “desktop Linux”. For one, it being a hand-held system will reinforce that difference, and people aren’t as willing to tinker about with their handhelds as people are with their desktop systems. Steam Deck’s OS might as well be BSD or even Temple OS as far as the ordinary user is concerned. I am hoping I am wrong here, however, as interoperability might make a difference here: if people can install and use their desktop programs to their Steam Decks in as much the same ease as installing an Android app in their phones, then perhaps the choice of OS here will make an impression on the users and not just the tinkerers.
Despite saying all that, however, I still think Linux is undergoing a renaissance. There’s quite a lot of improvements going on even as we speak. Usability, in a very general sense, like being able to daily-drive Linux without being hampered by a lot of issues, is way better than it was when I first used a Linux machine in a school computer laboratory close to twenty years ago. Advances like this is starting to pull people who are curious, interested, and already leaning towards making the jump—and if this trend continues, will lead more people into using Linux, leading to more people contributing towards advances, and so on.