At one point it seemed like there was just no stopping the Steam Deck but now it seems after being available for 1 year and around 8 months or so, the Steam Deck has started to move down the top sellers on Steam.
That was one heck of a run though right? Going over Valve's own Weekly Top Sellers list from the Steam Deck release up until the week of "Tue, September 26, 2023 - Tue, October 3, 2023", the Steam Deck was always globally in the top 10, where in that week it hit 11th place and the following week "Tue, October 3, 2023 - Tue, October 10, 2023" it hit 15th place. So that's around 83 weeks in the top 10 globally.
Keep in mind Valve's top seller list is by revenue, not units sold. Quite a number of those weeks (around 22) the Steam Deck was even in the number 1 spot globally. Coming up against games that were repeatedly selling in the multiple hundreds of thousands, and in many cases millions, that's a lot of Linux-powered Steam Decks going out into the hands of gamers.
That's only globally though, when going to different regions, the Steam Deck is still in the top 10 for some, but the opposite is also true, in some regions it's also much lower.
Given that handheld PC gaming is still quite a niche overall, with a lot more competition now from other vendors and with rumours swirling of an upcoming refresh, it's perhaps not surprising to finally see it start to slide down a little.
The Steam Deck only continues to mature and get better over time too, with lots and lots of Proton updates improving game compatibility and SteamOS 3.5 now in Preview, there's still constant excitement for the Steam Deck.