The original Hebrew Bible was the Torah (first five books of the now-Bible). That's it. Every book that was taken out, such as the Gospel of Thomas and all the Apocrypha, was taken out because it was deemed as uninspired by God at the Council of Trent (or Nicaea, I forget). That's when the first 66-booked Bible came to be (and the Catholics have their own Bible).
This is not necessarily true.
Divine inspiration was not necessarily the main reason for inclusion in the Bible. One could say it was not really all that much of a point.
The most important was whether or not the scripture had survived in the archives. Many scriptures existed in fragmentary or damaged form. Part of the job of the council was not just trying to figure out which books to use - but also what was usable within the surviving scripture.
Consider that some of the scriptures were literally traced back to fragments - fragments of different languages and eras stitched together to form a semi-coherent complete text if you were lucky enough to have proficient translators for those languages.
Since then, more surviving fragments (and near-complete scriptures) have been recovered. Missing scriptures have been found, and works predating the scripture used during the council's decision have also been found.
At the time, though, there was not the massive volume of scripture that we have today.
One of the other reasons to include/exclude came in the ability to verify the origins of the scripture. Did other scholars mention this scripture existing? Is the author known?
You also had political factors. The goal of the Bible was to create a standardized text for the Christian faith. You had the Gnostics in one part of the world using completely different sets of scripture from the Byzantine churches who were using different scripture than what the Coptic churches were using.
Excluding books that were very popular in a set of churches wouldn't be as bad (as they could always provide them as an addendum) - but INCLUDING books that groups of churches in one area deemed heretical would be a good way to fracture the church.
Including Revelations was about as risky as they chose to get aside from their decision to include the Gospel of John.
So, from a political standpoint - it was more risky to include books than it was to exclude them. Thus, the Bible can be thought of as a "bare minimum platform."
This is why other churches still included additional books for some time. The Book of Enoch is particularly interesting and used to be very common in many bibles.
The issue of "divinely inspired" is basically a catch-all phrase meaning the above issues rolled into one nice phrase.