The life of Jesus parallels the life of Mithras some 250 years earlier. It could all be simple propaganda to win over followers of Mithras.
What are you referring to as 'propaganda?'
Christianity changed the world, Junior, and it is because of the truth of the Resurrection.
The Romans were afraid of it, and they tortured and crucified the followers of Jesus, who showed only love. Why were they willing to die for a complete lie?
It is part of the historic record that Jesus was a very real person (and I just found out there is more written on his life than there is on the life of Winston Churchill........interesting, no?)
There were eyewitness accounts of His life, His crucifixion and His resurrection that were written down before those who witnessed it died.
There is more than ample proof that the Gospels are authentic (one proof of an ancient text is whether or not in contains embarrassing material for the author. The fear of the disciples following the crucifixion would not be there if they were only proselyzing).
If you believe that Caesar wrote the Gallic Wars, and Plato the Republic, then you should believe in the historic Jesus.
You can reject the truth of what Caesar said, or disagree with Plato, or call Matthew, Mark, Luke (correction from a previous statement I made.....he was not an eyewitness) and John liars, but you cannot deny that they wrote authentic historic documents, and it behooves you to study them as such.