MS-DOS was before MS Word and Excel. It took a long time for Word or Excel to really gain ground against the market leaders, and arguably they weren't really dominant forces until they were packaged together as Office in the 90s.
Windows NT may have started development in the late 80s but it certainly wasn't released until the 90s and took a while to find success.
You also miss out on the main reason Microsoft was able to become a dominant force in so many fields; MS-DOS. DOS was the PC operating system from the 80s into the 90s, until Windows 95 finally took over, and gave Microsoft the money and position to do whatever it wanted.
None of the rest of its software suite would have become dominant without being built on top of DOS and later Windows.