" None of those words attributed (in the synoptic gospels) to Jesus said Jesus required belief in the resurrection of Jesus! " Good point !
"Mark" was the first Gospel that we find in the N.T to be written, Matthew and Luke copy "Mark" word for a word to a great degree, and then add their two cents. The "Long Ending" to Mark is a later addition, because "Mark" lacked any real reference to the resurrection as significant perhaps.
This reluctance to include BELIEF in the Resurrection as vital to being saved is not really contradictory to the earliest teaching we have on Christianity in the N.T, that of Paul, but of course, if one denied the FACT of the Resurrection, that person would be automatically an Apostate from their Brethren's point of view.
So Mark Jones' summary of the Good News is not so far off, it was a simple message, which is why it had such appeal, and why Christianity spread like a flame in dry tinder.
Jehovah's Witnesses do not preach this simple message, they add to it, complicate it, and make it not just less effective in promoting Christianity, but ruin it.