Yeah I believe they are not entirely fabricated. There was a historical Jesus who had a following. A lot of the listed details are up for debate but the core of it is too hard to fabricate well enough to fool modern biblical scholars.
The Book of Daniel is from the 2nd century BC but it claims to be from the 6th century BC predicting events through to the 2nd century BC and beyond. One reason we can tell is the language usage and how the predictions are spookily accurate until the 2nd century BC and then they get way off. It was good enough to trick the people deciding the biblical canon so they included it even though it was written way later than all the other books, but not good enough to trick us in the 21st century AD.