There is no reason to assume Jesus was not real. This issue was closed by historians over a hundred years ago and never has there been thrown any new light that puts it into doubt. It’s only fringe people with specific agendas, who always seem to lack the skills and knowledge to work with the sources, who claim otherwise.

For a good overview of why historians know Jesus existed you should read John P. Meier - A Marginal Jew: Rethinking the Historical Jesus, Volume I: The Roots of the Problem and the Person.