Second, and most important, these books were accepted because they were believed to be inspired by God.
For example, the authorship of the Book of Hebrews is unknown, but the book was accepted without serious questioning because it bears the unmistakable stamp of the transforming power of God.
Of course, the book had to be consistent with previous revelation.
But closer inspection showed that the providence of God was so evident in the story that it had the authenticity that gave it acceptance. For example, Paul in the New Testament argued that his message was authoritative because he was an apostle, “not sent from men, nor through the agency of man, but through Jesus Christ, and God the Father” (Gal. The Book of 2 Peter was disputed in the early church because some doubted that it had been written by Peter.
The writing style appeared different from 1 Peter, hence the doubt.