they literally want to tap into people's onedrive accounts

But enough about Microsoft! 😉

As far as I can tell there aren't really any rules anymore if you annoy rich people enough. They just sort of come after you regardless.

I would assume they have some sort of case open in the court system to try and punish the leaker, and are requesting a subpoena to get info from Microsoft as part of trying to track the leaker down.