Contrary to common belief, there was never a one-time, truly universal decision as to which books should be included in the Bible. It took over a century of the proliferation of numerous writings before anyone even bothered to start picking and choosing, and then it was largely a cumulative, individual and happenstance event, guided by chance and prejudice more than objective and scholarly research, until priests and academics began pronouncing what was authoritative and holy, and even they were not unanimous. Every church had its favored books, and since there was nothing like a clearly-defined orthodoxy until the 4th century, there were in fact many simultaneous literary traditions. The illusion that it was otherwise is created by the fact that the church that came out on top simply preserved texts in its favor and destroyed or let vanish opposing documents. Hence what we call "orthodoxy" is simply "the church that won."
Astonishingly, the story isn't even that simple: for the Catholic church centered in Rome never had any extensive control over the Eastern churches, which were in turn divided even among themselves, with Ethiopian and Coptic and Syrian and Byzantine and Armenian canons all riding side-by-side with each other and with the Western Catholic canon, which itself was never perfectly settled until the 15th century at the earliest, although it was essentially established by the middle of the 4th century. Indeed, the current Catholic Bible is largely accepted as canonical from fatigue: the details are so ancient and convoluted that it is easier to simply accept an ancient and enduring tradition than to bother actually questioning its merit. This is further secured by the fact that the long habit of time has dictated the status of the texts: favored books have been more scrupulously preserved and survive in more copies than unfavored books, such that even if some unfavored books should happen to be earlier and more authoritative, in many cases we are no longer able to reconstruct them with any accuracy. To make matters worse, we know of some very early books that simply did not survive at all (the most astonishing example is Paul's earlier Epistle to the Colossians, cf. Col. 4:16), and have recently discovered the very ancient fragments of others that we never knew existed, because no one had even mentioned them