Comment by jazzypants

I think the first shift was the reckoning with Windows NT actually being decent software. Windows 2000 (AKA NT 5.0) included Active Directory, WebDAV support, and a host of other features that were genuinely useful in a sysadmin setting [0]. Also, it shipped with IE5 which introduced XMLHttpRequest and was the best web browser by a mile. Between their pushy sales reps and so much stuff being included by default, I think it got kind of hard to push for anything else for a while.

https://en.wikipedia.org/wiki/Windows_2000