Agreed, the premise here is in my opinion pretty wrong. While it too would be a little hyperbolic, I’d be much quicker to argue the opposite.

Also, how successful other OSes were or weren’t at attracting an install base during the 1990s is very tangentially related to why Copland failed.

Slightly related: I’ve always wondered what Apple might be like today if Gassée had succeeded in selling BeOS to Apple instead of Jobs with NeXTSTEP. Probably a nice headstone in the Silicon Valley graveyard next to Sun, SGI etc, but interesting to consider.