Open vs. closed is perhaps misleading, but at the very least it's obvious that MS targeted high-volume sales with Windows while Apple targeted low-volume sales with the Mac / Mac OS. Apple built in a huge profit margin on its end-to-end system, putting it out of reach of much of the market. MS built in a smaller per-unit profit on its OS, but since the incremental cost of software is negligible this put them in a much better position since increased volume increases their profit margin almost without limit.
Microsoft also had a first-to-market advantage with early versions of Windows, and they also gained from almost no productivity app competiton back in the 1990s.
So what you're saying is further multiplied by all the businesses who chose Win 95 over Mac OS 8, then stuck with Windows when upgrading their equipment.
