More than likely, I'm not the only person whose first reaction to the Steam Deck was something along the lines of "didn't Valve already try this?" Valve's hardware products have really run the spectrum from the VR gold standard Valve Index to the less impressive console-like Steam Machine. Sure enough, Valve say that "Steam Deck feels like the culmination of a lot of that earlier work." They say that Proton has been the route to help them solve the "chicken and egg" problem that the Steam Machine fell victim to.
In another interview with IGN, three Steam Deck designers sit down to talk about how the Steam Deck was a puzzle that required solving both hardware and software issues. On the hardware side, they felt that it's only been recently that a handheld device like the Deck could really be expected to play the newest games on their intended settings. Even with handheld-size tech sorted, software has been a sticking point for their hardware plans in the past.
"Steam Machine was a really good idea," says Greg Coomer. "The operating system wasn't quite there. The number of games that you could play on the system wasn't quite there." Despite those shortcomings, Coomer says "I don't think we would have made as much progress on Steam Deck if we hadn't had that experience."
Scott Dalton talks about the "chicken and egg" problem of the Steam Machine, which needed both enough games playable on Linux to make the device worth owning and enough device owners to make supporting it worthwhile to developers. "That led us down this path of Proton where now there's all these games that actually run." Proton is Valve's compatibility layer allowing Windows games to run on a Linux machine like the Steam Deck.
"It was really important for us to be able to talk directly to developers and say 'hey look, the Steam Deck runs your game. You don't have to port,'" says Lawrence Yang.