Maybe AD, but honestly it feels more due to strong marketing and relationships with enterprise companies. My three most recent projects were all Azure based, no one could justify why Azure other than "that's what the customer wants".

In my experience yes. between 2012 and 2015 i did an on prem to office 365 migration every couple of weeks on average working for an MSP.

The pitch is just so insanely easy when speaking to management/finance types. You can remove so much financial ambiguity which comes with maintaining servers or expanding a business.

Every Finance director i spoke with loves being able to model costs years in advance.

Could also be due to the fact that Amazon might become a competitor in the future. Take the banking/finance sector, it might not expect competition from Microsoft, while Amazon could decide to enter the market, having a much more 'entrepreneurial' spirit.

I guess mainly because of o365.