Old Testament Prophecies Converge

Why would Jude quote Enoch rather than the prophets? Heiser puts the question in exactly those terms - was the point "to affirm what is written in Old Testament narrative or to give the book of Enoch authority?"
His answer: "I think it's to affirm what's written in Old Testament narrative."
And he gives the practical reason. 1 Enoch 1:9 "combines several apocalyptic ideas from the Old Testament that otherwise Jude would've had to cite three or four different passages to make his point." Heiser names them: Jeremiah 25:30-31, Isaiah 66:15-16, and Zechariah 14:5. One sentence from Enoch did the work of three prophetic citations.
Scripture links:
- Jude 14-15 - The quotation, doing the work of three Old Testament passages at once.
- Zechariah 14:5; Jeremiah 25:30-31; Isaiah 66:15-16 - The texts standing behind it.
Jude was not granting Enoch authority. He was reaching for a convenient summary of the prophets.