Judas knew the prophetic gift had ceased (1 Maccabees 9:27), so he likely gathered the scattered Scriptures and sorted them with an order and number, giving us the first firm division of the Prophets and Hagiographa but also the traditional order and number of books within.
(The Origin of the Bible: Newly Updated by F. F. Bruce, J. I. Packer, Philip W. Comfort, and Carl F. H. Henry, 2020. Biblical Languages by Larry Walker. Section One: The Authority and Inspiration of the Bible. Page 5-6; The Canon of the Old Testament by R. T. Beckwith. Page 56-60)