Graphical User Interfaces were important. So was cost control. Just what must an OS be?
Everyman wanted a GUI. Everyman had money, though, for a more modestly priced computer. Even the cheaper prices of latter Macs could not overcome the high prices paid for common peripherals.
And so it was that the majority of the world learned Internet use and those oddball apps, like 'email', on Windows 9x.
The OS must be the hub of several spokes:
OS/2 never got the entire formula right. It and many others are gone.