Why are the words of these prophets not preserved, if they spoke Gods word?
First question: Several of the prophets you listed are not stated as having their own books, but their “words” were simply the spoken word. As far as why any books of theirs may not have been preserved, if they had them, then I would have to go with “only God knows.” Concerning the book of Enoch (as it is a special case), Jude refers to his words and was likely referring to the book of Enoch, which is still preserved, but it is a pious forgery and not actually the words of Enoch himself. Jude may or may not have known this to be true, but at this point in history to quote the book of Enoch would be the equivalent to saying that Enoch himself said it. Second: All because a source is credible doesn’t mean it was necessarily “inspired.” The fact that we have biblical authors showing that they used sources, however, shows something about the bible’s credibility, I would say.
