I think the article's thesis is muddled. BeOS and OS/2 technically "succeeded", in the sense that they were developed into a working, usable state, but they were commercial failures. They still exist today but they're dead ends. Neither of them dominate the world.
While Apple was struggling with Copland, Microsoft was struggling with Cairo, which had a similar fate; it mostly evaporated, leaving a few interface elements behind. Even though NT had greater market share in the late 1990s than the entire Macintosh platform it was a speck compared to Windows 3.11 and 95/98. Windows XP wasn't really finished until Service Pack 2 in 2004, at which time Microsoft was struggling with WinFS, which failed, and Longhorn, which eventually became Vista. It was difficult for Microsoft as well.
Writing a general-purpose operating system for a mainstream audience is hard - writing it without going bankrupt, or without taking so much time that the computing world moves on to the next thing, is almost impossible. The majority of operating systems developed in the 1980s and 1990s are now in the same state as the Emperor of Humanity in Warhammer 40,000, e.g. dead but a few cells are kept alive by the efforts of hobbyists. This is the fate that has befallen MorphOS, RiscOS, TempleOS, whatever remains of Palm etc.
In that respect Apple did pretty well. Unlike Microsoft they weren't flush with cash from Office and Windows. They had one major catastrophe that almost destroyed them, but they turned things around. I'm not an expert but impression is that Apple's development of OS X and latterly MacOS has been relatively smooth - bear in mind that during the same timescale Microsoft went from Windows 95 to Windows 10, which is perhaps more impressive given the enormous ground they covered, but ye Gods think of the waste. Mac fans grumbled about Lion but it was nothing compared to the reception that Vista and Windows 8 had.
And, yeah, while I'm still drunk I maintain that under the skin Windows 8 was actually okay. It was okay! You were okay, Windows 8. It ran better on the same hardware as Vista and at least it had a proper design instead of looking like a rave album cover. It's just that Microsoft screwed up the start menu. Everything else, great! 2gb of memory, no problem. It ran on my old ThinkPad X60 without a problem.