Interestingly, the Christianity that exists now, the Christianity that revolves about the gospel story of a Jesus of Nazareth and its climactic empty tomb ending can be traced back to the third century. Prior to that, Christianity was far more nebulous and varied.
Just because Christianity was far more nebulous and varied does not mean that many Christians didn't accept the Gospel stories. We know that they were widely circulated, by the second century. And from what we can tell, the majority of Christians used at least one of the Gospel stories. So it can actually be traced back to the first century, before Mark was actually even written, when the story was still just part of the oral tradition.
More so, the Christianity that exists now is not the same Christianity that existed in the third century. They are vastly different.
The gospels read of a Jesus of Nazareth that was crucified during Pilate's time, but the earlier epistle writers don't give us so much as a clue or a hint of this, and nothing of an empty tomb. There are no non Christian sources for this character that supposedly drew huge crowds wherever he went either. The Christianity that revolves about the gospel story is very different from the early Christianity that existed before the gospels became known, and there is no indication that the gospels affected Christianity as a whole until the end of the second century, it appears to have taken that long for the gospel stories to take hold.
All this shows is an ignorance towards what the epistles are. There is no wonder as to why the epistle writers didn't mention details of Jesus. They simply were not very interested in those aspect. Paul was more interested in the resurrected Jesus, as to him, that was what was important. He wasn't a historian, he was a theologian.
Paul was simply writing letters to different congregations that had asked questions or problems had arose in. There is no reason to assume that they would take time out of their theological endeavors. It simply did not fit into what he was doing. And really, it would have been out of place. Paul gives us little detail about anyone. He doesn't he tell us much about himself.
However, we do know that in the oral culture, the Gospel stories were already widely circulating. We know this because of where the Gospels appear. Even shortly after they are written, we see them being mentioned by more influential groups in the movement. We see Papias, in the early part of the second century, even discussing it. By the early second century, all of the Gospels had been accredited to. We even know that some of the Early Church fathers (late first to early second century) were aware of the Gospels and quoted parts of them. This shows us that they did play an important part even during the end of the first and early second century.
More so, there is a thing called exaggeration. The Gospel writers, who were not writing biographies in the strict sense of the genre, exaggerated incidents. More so, being an oral culture, that is something we can expect, to a point.
Finally, we do have Josephus, writing in the same century, speaking of Jesus. It is no wonder it took some time for others to start writing about Jesus though. He made a very little impact in an area that wasn't very much cared about.
Second century Christian apologists weren't anymore knowledgeable of Jesus from Nazareth than the first century Christians. Athenagoras makes his beliefs known, Christ for him is a sky god:
First, Atenagoras wrote during the second half of the second century. This is nearing the time that you state that the Gospels stories start effecting Christianity as a whole. So it actually doesn't support your point. Especially when we see at least four Gospels circulating, and being discussed by the early Church fathers, who were influential, in the late first to early second century. We even see by around 140 C.E. a canon being formed that uses at least one Gospel. By 160 C.E., Irenaeus refers to a four Gospel canon. A little research shows your comment to be unfounded. You can't use one example to prove your point here.
Unfortunately, in the course of 37 chapters, Athenagoras neglects to tell the emperor that Christians believe this Logos to have been incarnated in the person of Jesus of Nazareth. He dissects contemporary Platonic and Stoic philosophy, angels and demons, as well as details of various Greek myths, but he offers not a scrap about the life of the Savior. [/I]
One problem here. This Logos being incarnated in the person of Jesus of Nazareth is only present in the Gospel of John. All this suggests is that Athenagoras did not use the Gospel of John. You can't imply anything else from that.
Empty tomb indeed. But let's cut the early gospel writer of Mark some slack, after all he was writing metaphorically, not historically.
Understanding the genre would greatly help you in this case. Knowing a little about Christian history would also help.