There are many people who believe Jesus never existed and that he is just one of the many fictional characters of the novel titled "the Bible".
Yet these same people follow a calendar starting on Jesus' birth year, many of them have a name that is derived from one of Jesus' apostles (e.g. Paul, John, Luke, Matthew, Mark, etc.) and they believe in many of the radical teachings of Jesus, like love your neighbor.
Jesus' imprint on the world is undeniable. Just consider that in 2015, there were about 2.2 billion Christians. That’s significantly more than the 1.6 billion Muslims, yet no one questions the historicity of Mahomet. By the way, the Koran contains five times more references to Jesus than to Mahomet, and Muslims consider Jesus a historical character and one of the greatest prophets that ever lived. Jesus is also referred to in both Jewish and Roman history books.
If Jesus never lived, how can you account for all the foregoing? How could a fictional character from a very old mythical book have left such a lasting impact?
A final thought. One has to admit that the teachings of Jesus are amazing. No one spoke like this before or ever since. And billions have been inspired by his words over the last two thousand years. If Jesus is but a fictional character, then who is the master who came up with the life changing guidance found in the new testament? No one else stood up to claim authorship.