They stand to make a very large amount of money from having everyone using Microsoft apps and services and with all their usage data and email/contacts contents

They stand to make a very large amount of money from having everyone using Microsoft apps and services and with all their usage data and email/contacts contents being sent back to the mothership. I think that's why they did it, and why they've done similarly laccidental' things over the last couple of months. All other reasons are secondary.