You are overestimating the effects. Or just forgetting what the situation really had been.
* MacOS had not been thrown out and replaced by a Unix derivative until very late in the game.
* there had been AmigaOS, which was also not a Unix by any stretch of imagination. Might or might not have died off; hell knows.
* IBM mistake of using Intel's design failure (286 protected mode architecture) would still have happened. Results wouldn't have been any prettier than in real history. By the time Intel has fixed the worst of that it was too late - OS/2 interfaces had been deeply affected by that horror and it was too late to fix them.
* Gary Kildall and his pile of garbage. That's the guy you have to thank for the mess, far more than Gates&co. A lot of bitty-box software had been out there and it had been cheerfully ignoring the nearly inexistent kernel. Porting _that_ to anything resembling an operating system would have been slow and painful.