Since historically Linux usage hovered around 1%, I'm guessing that the Steam Deck by itself didn't drive any additional users to Desktop Linux (or at least not in huge amounts), though the 1% by itself is probably driven by Valve's efforts to improve Linux support.
You don't have to guess, just look at the steam hardware survey - https://store.steampowered.com/hwsurvey?platform=linux - 44.18% of Linux is SteamOS Holo (a.k.a. Steam Deck), while overall Linux is 1.82%.
Since historically Linux usage hovered around 1%, I'm guessing that the Steam Deck by itself didn't drive any additional users to Desktop Linux (or at least not in huge amounts), though the 1% by itself is probably driven by Valve's efforts to improve Linux support.