My anecdata is that Microsoft used salespeople to talk to executives and give them a deal on Azure so good they couldn't pass it up.
Still doesn’t change the fact that Azure isn’t a great platform to use, though.
Repeat for Random windows server to Azure and again for Office Live.
Ohh, you can ru Linux too and do most things people are doing with AWS.
It’s a pretty easy sell to me (and worked pretty well on the F100 company I work for).
The migration from on-premise WSAD and Exchange to Azure AD and Office 365 is pretty painless - and once you've done that why wouldn't you use the rest of Microsoft's cloud based platform. That's the big advantage Microsoft has for most enterprise customers.