The whole OS/2 Windows fiasco was a perfect opportunity for someone else to jump it.
IBM and Microsoft fought on the direction OS/2 should take and it took far longer than was expected. Then Windows 3.1 made a surprising breakthrough and all the software developers had to ditch their OS/2 versions and go back to Windows. It's what killed Word Perfect as the dominant word processing company.
If Windows 3.1 wasn't quite as successful. And if someone had another option lined up and pushed it, it might have taken off.
Let's say Dell loads GEM on all their computers, and then Digital Research figured out a way to put that GEM environment on top of a Unix variant, so fully GEM compliant software could now properly multitask...
I think that requires 2 PoDs. Windows 3.1 not taking off, and DR having a better way forward. Given those two, Dell, say, might well have jumped ship.
It's hard to remember now, but early versions of Windows were a real kludge, and not a major threat to anyone.