See the Atwill link above.
It's hard to overstate the stupidity of the premise. The Gospels themselves record that the Jewish leaders were all deadly enemies of Jesus and that Jesus had confrontations with them. Why would that persuade the Jews to adopt this "new" Judaism?
Then there's the other books of the New Testament. They repeat many of the themes of the Gospels, such as Jesus' resurrection. Some of them refer to people mentioned in the Gospels (besides Jesus). If the Gospels are elaborate fictional accounts, then some of the New Testament books refer to people who didn't exist. What in the world was going on there? Note that the conventional dating of the other NT books is earlier than the Gospels. How does that fool account for those books?
Those are just the first couple of huge problems with his ludicrous idea.