This is the MS justification
Microsoft has been trying to gain control of the sites for two years. In court documents, its lawyers filed a complaint on Aug. 13, 2016, alleging violations of the Computer Fraud and Abuse Act to harm Microsoft and its customers.
The complaint alleges that two unknown individuals led the effort "to direct attacks against targeted networks, to infect computing devices connected to those networks that permit Defendants to compromise the security and conduct reconnaissance of and move latterly through those networks, and to locate and exfiltrate sensitive information."
They also accuse the individuals of accessing the computers and networks of Microsoft customers, intercepting communications via Microsoft's Windows operating system, making unauthorized use of Microsoft trademarks, "trespassing" on the computer networks of Microsoft and its customers, intentionally interfering with Microsoft contracts and profiting unjustly from their unauthorized use and access.