um hier mal den Lehrer zu spielen. das ist ziemlich falsch. die realität ist (was office auf mac betrifft) die folgende:
Windows was the last platform supported for each of Word, Excel, and Powerpoint. Those applications were ported to Windows. Word was ported from Atari ST (itself, originally a port from a UNIX variant), Excel and Powerpoint were ported from Mac OS.
The one application that they "ported" to Mac was Outlook... Which wasn't so much a port as they developed and released the Mac OS, MS DOS, and Windows 3.11 versions simultaneously.
Microsoft could have dropped support for Mac at some point, but stuck with it because of unrelated anti-trust litigation that they were fighting for quite some time.
The Mac unit remains one of Microsoft's few profitable divisions at MS, so they won't get rid of it unnecessarily.