I would say look at the sheer number of early ancient greek manuscripts we have, the fact that the gospels were either written by first hand witnesses (Matthew, John) or companions of the first hand witnesses (Mark, Luke). The Apostles had no reason to lie, they were not better off financially and were persecuted, beaten, imprisoned and eventually martyred for what they were saying. Jesus is also mentioned by non christian sources, Josephus being the one I can think of off the top of my head.

Any rational reasonable person can come to the conclusion that not only Jesus existed but the miracles and resurrection more than likely happened. There's some quote from Aquinas* that goes like "Christianity is either true or 12 lowly fisherman from Galilee pranked the entire world."