the supernatural, obviously, is made up, but the most current secular historians centre around Jesus and his core teaching being based in fact. not least because there are a good deal of his teaching that are inconvenient and which no-one trying to create a religion would have invented out of thin air.

see: pretty much anything written by Bart Ehrman

even Carrier, the “golden boy” of the myth point of view, says he calculates a 2/3rds probability that Jesus was not a myth.