alt Hacker NewsSteam Deck was made possible by their ongoing efforts to enable the play of most of their games catalog on any hardware platform that is computationally capable of running them, regardless of OS or architecture.
The end game for Valve isn't Steam Deck 2 or 3 (which is statistically impossible for Valve to produce), but for Steam to be on everything.
Steam Deck was made possible by the plethora of the Windows games developer market and Proton.
Most of the studios that own those games, and target POSIX like OSes on mobile phones and game consoles, are yet to bother with GNU/Linux versions for SteamOS.