Please forgive the long answer.
The author of Enoch is anonymous. He doesn’t identify himself--he acts as a redactor or “editor.” The book starts off with, “The words of the blessing with which Enoch blessed the righteous chosen who will be present on the day of tribulation, to remove the enemies; and the righteous will be saved."
So the author is anonymous--which was actually a common ANE (Ancient Near Eastern) practice.
Actually Enoch is a collection of several separate works. Some have dated the oldest section to 167 BCE (see Encyclopedia Britannica) during the time of the Seleucid (Greek) control of Israel. As noted in the original article, some even speculate some sections were written much later: in the 2nd Century CE (or AD).
From the forward of my English copy of Enoch (translated in 2012)*:
“1 Enoch is a collection of apocalyptic (revelatory) texts that were composed between the late fourth century B.C.E. and the turn of the era.” (Nickelsburg & VanderKam, Forward The Hermenia Translation: 1 Enoch).
Now to answer your question about why many ancient mss were anonymous:
According to a 2008 article by Amin Baum in Novum Testamentum, "The Anonymity of the New Testament History Books: A Stylistic Device in the Context of Greco-Roman and Ancient Near Eastern Literature”:
"The authorial intent of the Gospels' anonymity can also be deduced from its ancient Near Eastern and OT background. Unlike the Greek or Roman historian who, among other things, wanted to earn praise and glory for his literary achievements from both his contemporaries and posterity, the history writer in the Ancient Near East sought to disappear as much as possible behind the material he presented and to become its invisible mouthpiece. By adopting the stylistic device of anonymity from OT historiography the Evangelists of the NT implied that they regarded themselves as comparatively insignificant mediators of a subject matter that deserved the full attention of the readers. The anonymity of the Gospels is thus rooted in a deep conviction concerning the ultimate priority of their subject matter.” [From the abstract--emphasis mine]
Baum is speaking primarily about the anonymity of the four gospels. While non-canonical books, like Enoch, were not regarded as authoritative, they still followed the same tradition of the literature of that era.
Note: letters (epistles) are different types of literature where the name of the author is important because of its nature.
Most letters (including secular letters) in the first century identify their authors by name (e.g., “I, Paul...”, “Peter, an apostle of Christ to the chosen ones from...”, etc.).
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*Note George Nickelsburg is professor emeritus of religion at the University of Iowa, author of Jewish Literature between the Bible and the Mishna and James VanderKam is professor of Hebrew Scriptures at Notre Dame. He is the former editor of the Journal of Biblical Literature and he has edited The Jewish Apocalyptic Heritage in Early Christianity.
