I would honestly like to read a treatise on why investment comes with Apple platforms first even though other platforms were there first, but we see it time and time again. Vision Pro is probably the first time that has faltered.

My guess would be it's a combination of Apple users spend more money, some chauvinism among investors (they all use Apple platforms), and that it's the largest single development target (android fragmentation is still real when it comes to messier stuff like hardware access and background tasks)

Apple Watch was at least as much as a platform failure as Vision Pro, though much of the story for the latter is yet to be written.

I think there have been many small, successful hardware products. It's just that they look like relative failures or accessories to mobile phones in comparison because iPhone (and to a lesser degree smartphones in general) is just a colossal success and uniquely able to absorb so much new functionality.