Whoever made this decision had to have a recognized and accepted authority to do so given to them by someone who had the power to do so. Otherwise, anyone could claim to have that authority and make any list that pleased them.
So the question to answer first is: Who had the authority to decide the canon? To go about the task, however long it took, to include some books and exclude others. Find out who that is, and what canon they used (or still use); and then-- viola-- you will find your canon.
Yes, I believe in inspired scripture, but I am still looking for men and councils who had inspiration equal to that level of inspired scripture.
I have found none. There are none.
No man or men or council can become Absolute Beings and with Absolute Certainty compile books together - and we can see this with the oldest available Codices (Codex A, S and B) and the Clermont List and Muratorian fragment.
And no note has ever been sent down by God attached to a compilation saying, “Here is your inspired List and Codex.”
We have relied on men and they failed us.
The men who wrote inspired scripture didn’t fail, but those attempting to decide what books to bind together failed us even as early as 180 A.D and in 300 A.D and with the earliest available Greek manuscripts left today - Codex A, S and B (Vaticanus).
If only those in the Apostolic Age had formally as books were being written and decided which OT and NT books were and weren’t meant to be bound together...