To clarify, the thesis I lay out in my book is that there was no narrative about Jesus or belief that Jesus was a real person until the Gospel of Mark was written. The story of Mark is what created the belief that Jesus was a real person. The writer of Mark was not working from existing accounts of Jesus, the writer of Mark invented the entire narrative himself as an allegory, which was later misinterpreted as a literally true story, mostly because of the revised version called Matthew.
To clarify, the thesis I lay out in my book is that there was no narrative about Jesus or belief that Jesus was a real person until the Gospel of Mark was written. The story of Mark is what created the belief that Jesus was a real person. The writer of Mark was not working from existing accounts of Jesus, the writer of Mark invented the entire narrative himself as an allegory, which was later misinterpreted as a literally true story, mostly because of the revised version called Matthew.