Valve's insane corporate structure means its strategic moves are plain as day. They initially went on OSX because it made sense to leave no room for a competing game market to start on Mac and move to Windows.
They've invested massively on Linux and have attacked the problem from two angles in the last ten years because they need to diversify. They can't single-handedly rely on Microsoft for their continued existence. Hence the VR headsets, the Steam Machines, and now the Steam Deck.
They've put zero effort on macOS on Apple Silicon because they would gain nothing strategically, and the percentage of Mac users using Steam is small. The hardcore gamer on a Mac does not exist. We have consoles.
It's not insane for them to be transparent. When Valve depreciated Steam Play for MacOS, they had engineers very clearly spell out the reason: the MacOS runtime is not stable enough for games. They also called this out when depreciating SteamVR for MacOS, it seems less like a "strategic move" and more like a platform limitation.
There's definitely something for Valve to gain by porting Steam to MacOS, after all they did support MacOS with Proton originally. The work required to fix it for modern MacOS is monumental though, and unless Apple sponsors it I see no reason why it would happen. Once they axed 32-bit execution support on Mac, there was effectively no reason to keep supporting the platform anymore gaming-wise. OpenGL depreciations were the icing on the disappointment cake, very clearly Valve was being told to pound sand by Apple.
They've invested massively on Linux and have attacked the problem from two angles in the last ten years because they need to diversify. They can't single-handedly rely on Microsoft for their continued existence. Hence the VR headsets, the Steam Machines, and now the Steam Deck.
They've put zero effort on macOS on Apple Silicon because they would gain nothing strategically, and the percentage of Mac users using Steam is small. The hardcore gamer on a Mac does not exist. We have consoles.