The post-apostolic church had to deal with many writings relevant to its interests. There were documents they had inherited, and there were new documents being created. All these documents were being copies, because all copies had to be made by hand in the pre-Gutenberg eras – and that took time. So, there were lots of documents in circulation.
The early post-apostolic churches had to continually sift through all those documents seeking to keep and hold above all others those that came from the apostles. Remember that churches were spread all over the far-flung Mediterranean world. A document written in one part was not immediately ubiquitous in all. Over time, the churches came to consider all the apostolic documents as what came to be called the New Testament. As a result, the books came to be known as canonical.
In modern times as skeptical scholars began to question authorship of various New Testament books, believing scholars were not as zealous as they should have been in defending apostolic authorship. In one sense, they didn’t need to because the canon was closed. Nothing was getting in and nothing was going to be taken out. But that was a false sense of well-being. The writings of the New Testament are not authoritative for us because they are in the canon. Rather, they are authoritative because they are apostolic.
The Bible is the Scriptures of the Prophets and the Apostles. It is not the creation of the organized church. Rather, it is the creation of God Almighty through His servants the prophets and apostles. God grant that believing scholars recover a zeal for defending apostolic authorship of those 27 books.
If belief in apostolic authorship of the New Testament was good enough for the ancient church, it ought to be good enough for the modern one.