The growth of Christianity is not largely different than the growth of any other world faith. It is largely the result of heads of state forcing their subjects to follow their religion.
The biggest thing for me though is that the story of the disciples/apostles is very unique. They weren't being forced to follow Christ. They gave their lives for their commitment and level of "convince-edness" of what they had witnessed. That's a huge deal, in my opinion. They personally weren't trying to gain anything from following Christ, and even if they had, they stood to gain
nothing.
Just let that sink in - they died for what they had witnessed and
knew to be true. That's what the new testament documents. I'm not an expert on the branch davidians or Jamestown...I think someone had brought them up in this thread or the other...but I don't believe that those groups were claiming to be witnessing/doing the supernatural in their activities. Could be wrong about that, if so, please correct.