Pivoting to becoming more service oriented. Azure/Office365 are their next generation core. Azure as a development target, which pragmatically makes sense as companies with Windows services/apps move to the cloud. And Office365 in the same vein. Not to mention them extending office to other platforms, which combined with Office365 (email) makes a lot of sense.
All of that said, outlook integration to office365 is actually worse as a mail client than it had been in the past with self-hosted Exchange. Counts don't update properly when you "delete all" from a folder, and even then it's inconsistent. I know it's to allow for better scale/resource control on the servers but it's still very annoying to say the least.