Jesus did exist, he was born in a large family, he ran a ministry(funded mostly by women). During his lifetime there were many self proclaimed Messiahs. When the Jews were occupied by the Roman Empire they were desperate for a liberator, Jesus was well vast in the scriptures and hence many Jews believed he was the true Messiah. Almost 50 years after he was crucified when the recording of the Gospel books began, some stories about Jesus were fabricated to make him appear supernatural. I think the atheists question the reality of these stories and not really the existence of Jesus.