I Do Feel That This Verse Has Never Been Well Explained To Me.

 Jude 9 refers to a story in which the archangel Michael disputes with the devil about the body of Moses. Although the story cited by Jude has not been preserved, the literature of early Judaism contains several traditions that can inform one's understanding of Jude's source.

https://www.christianpost.com/voices/one-of-the-strangest-verses-in-the-bible-jude-9.html