Originally Posted by PsiCop

I don't know if I'm the guy you're talking about but I will take a stab at it nonetheless.

The reason people "waited" to write the New Testament books is because they hadn't yet developed their content, in the form we know them! That is, they were still in the process of coming up with doctrines, beliefs, rites and practices. The early decades of Christianity were dynamic and few things were settled. They were really not sitting around "waiting" to put their ideas down on parchment; rather, they were still working them out, going by earlier versions of those documents which no longer exist in tangible form.

The 7 "genuine" Pauline epistles were all written in the 50s CE, from about 52 to 58. (The other Pauline epistles in the New Testament were all later documents, retroactively attributed to him, but certainly not written by him.) If we take their author "Paul" at his word, he was writing after having converted some years before. All of these letters, moreover, address issues of doctrine or practice that had come up, after he'd been a convert and had been missionizing; they are all topical letters, then, dealing with matters that came up around the time he wrote them. So it's not really fair to say that he "waited" to write them. His letters are actually all very timely.

Around the 40s to 50s, another document was being sent around, now called "Q." This wound up being used as a source, later, for the synoptic gospels, and the Gospel of Thomas was a later version of it. Q grew from an existing oral tradition, one which goes back to the 30s, so again it's not fair, really, to say anyone "waited" to write it ... the content in it was, in fact, being transmitted (just not in writing until the early 40s).

Other source documents were also being sent around, again in oral form first, then written; these are the Passion Narrative and the Signs gospel, which were sources for Mark and John respectively. These are nearly as old as Q and probably were in written form by the 50s.

All of these documents had to have existed by the 50s, otherwise they could not later have been used as sources for the gospels, which were written from about 75 to 100 CE. One could ask, I suppose, why the Christians "waited" until then to write their gospels, but one must remember they already had these source documents to read, source documents which have subsequently been lost (because they were superseded by others, so that no one made the effort to preserve them).

Also, remember that the documents we have, are extant only because people preserved them. Scholars are very sure that many other documents existed by the 40s and 50s, they just didn't survive to modern times. Paul, for instance, almost certainly wrote more than just 7 epistles; but whatever those may have been, we have no idea, since they've been lost.

What survived, then, is merely a crude snapshot of what must have been a much larger production of proto- and early Christian documents. We know this, because the documents which survived, such as the canonical gospels, are dynamic and show the tracks of earlier documents from which they were composed. The problem is that ancient manuscripts are notoriously fragile, papyri were often re-used and re-re-used, and because copying them took a great deal of work, which was not undertaken unless a document was truly valued. This is why, for example, the Q document was lost; once its content ended up in Mark, Matthew, and Luke, no one bothered to copy it since it was already being copied as part of those larger works.

For information on all these documents, and to read them for yourself, go to Early Christian Writings.