How did they determine what was "inspired" if they were in disagreement? Did they just make it up?
Luther had some issues with some of the books (James and Hebrews) but you will find them in the Protestant Bible today.
Simple: they had to be Apostolic (i.e. written by one of the Apostles), and had "evidence of inspiration" (whatever that means). Trouble is, there were many such writings at the end of the 1st century -- almost 300 of them, all bearing names of apostolic authors.
The current books of the New Testament, Hewbrews, James, 2nd Peter, 2nd and 3rd John, Jude and Revelation were disputed, as to whether the authors were indeed who they purported to be, along a couple of hundred-plus others.
These other sources included the so-called "gospels" of Thomas, Hebrews, Peter, and the protoevangelium of James, and a variety of other works. They were rejected because they showed evidence of Gnosticism hidden in gospel-like language, or because they showed things that Jesus would have not taught, or simply because the style of the author purporting to be one of the Apostles was not the style of that Apostle's confirmed writings (which was one of the reasons the Revelation of John was kept out for so long).
The final result was that from all these source the Church selected 27 books as Scripture and rejected the rest. Maybe now you can understand why it took so long for the Church to give you the Bible you trust.
In addition, the Apostles used Septuagint as the OT source. If it was good enough for them, it is good enough for the Church. Unfortunately, the Protestants strayed and replaced the Apsotolic OT source with the Masoretic Text as the Old Testament, so we don't use the same Bible.