When they invested in Windows 1.0, their existing users were not asking for it and didn’t have a use for it. MS-DOS wasn’t a good foundation for a GUI, the IBM PC hardware was misaligned (e.g. terrible graphics), and obviously Apple was miles ahead.
The product didn’t fit any of Microsoft’s existing strengths and felt like a toy rather than a credible business tool. By the same logic that’s applied to AR/VR today, Microsoft absolutely should have exited the GUI market in 1988. (They were even a leading Mac software vendor! Why bother making their own worse GUI?)