Alexa caught him getting up to trouble
One of the employees with Amazon who does "quality control" for Alexa's listening in, err, voice command system, heard some things while listening to an Alexa recording. Instead of Diddy talk about his next album, he got an earful of all kinds of deviant behavior.
Amazon doesn't want people made aware that Alexa is always on and recording, and that those recordings can be listened to for "quality control purposes", so the Feds were tipped off anonymously.
The real truth.