Here is an interesting passage from the book cited in post #1 of this thread. Page 234.
"The New Testament writers certainly had no reason to make up a new religion. We must remember that all of them (with the possible exception of Luke) were Jews who firmly believed they already had the one true religion. And that nearly 2,000-year-old religion asserted that they, the Jews, were the chosen people of God. Why would the Jews who converted to Christianity risk persecution, death, and perhaps eternal damnation to start something that 1) wasn’t true and 2) elevated non-Jews into the exclusive relationship they claimed to have with the Creator of the Universe? And unless the Resurrection actually happened, why would they, almost immediately, stop observing the Sabbath, circumcision, the Law of Moses, the centrality of the temple, the priestly system, and other Old Testament teachings? The New Testament writers
I had to have witnessed some very strong evidence to turn away from those ancient beliefs and practices that had defined who they and their forebears were for nearly 2,000 years."