This is not unexpected.  Cybercriminals are fairly smart and they are motivated to target the resources with the greatest and/or most effective access.  As more and more of the world moves their respective Exchange and Active Directory resources to the cloud, O365 and Azure administrators move up the valued target list.

This article simply points out something we have known for some time.  We must take phishing threats and associated awareness training seriously.  This must become a priority for every organization, large and small.  This issue also places a brighter spotlight on the security associated with service providers and 3rd party administrators.  Make sure your security controls take those resources into consideration as well.

https://threatpost.com/office-365-admins-phishing/150352/