Pack of lies, really How so?
So to start with let's talk about the primary claim which is that a human was clinically dead for three days and then came back to life. There is no evidence that this has ever happened anywhere and it is physiologically impossible.
But let's for the sake of arguments accept that this did happen - in which case it would be, literally, just about the most astonishing thing ever to have happened.
So the second claim - that this impossibly astonishing thing was witnessed by 500 people (I gather all in one place) - were that to have actually happened it would have spread like wildfire. It beggars belief that were these 500 people to have seen this impossible thing that they would have kept quite - they'd have told everyone they knew and in a couple of tellings this would pretty well have covered pretty well the whole population. So it would undoubtedly have come to the attention of both the Jewish and Roman authorities.
Yet there is nothing - not a dicky bird from the supposed witnesses, from the greater population, and critically from the Jewish and Roman authorities, who were assiduous record keepers. Not a sausage.
Also were this to happen surely the population of Jerusalem would have undoubtedly accepted the early Christian belief and Christianity would have grown out of Jerusalem. But it didn't - it took hold elsewhere, not where those apparent 500 lived.
So for this all to be possible it would require those witnessing a completely astonishing event to simply ignore it, not tell all their family and friends. And also to ignore it theologically - saw a dead man come alive, says he's the son of god - but hey no biggy - I'll carry on with my existing belief. That simply defies credulity.