Well Microsoft never got anywere by making their software better then everybody else's. From
early versions of DOS, to Apple, to OS/2, to Novell, everything they made was done better by
They got 95+% of the PC market, business and personal, by making their products more
attractive, cheaper, and more profitable then other people's. Good advertising, correct
feature targetting, effective FUD, agressive salesmenship, manipulating other businesses,
giving big kick-backs to ISVs for convincing their customers to move to Microsoft, etc etc
etc. They are/were better businessmen.
In this case most businesses already massively use and depend on Windows, MS Office, Exchange,
Microsoft Server, Active Directory, and other Windows-only proprietary software. Sharepoint
integrates with all of that cheaply. It's a no-brainer to try it out and gradually use it more
and more as it matures.
Linux and open source software, on the other hand, while being much more technically superior
(especially in the web arena) require much higher amounts of investment in employees (which
are treated as a liability, not a asset, in the financial books) and changes to their
infrastructure to use.