from all I have read, both from believers skeptics, psychologists and others...the following seems to be what may have happened:
Paul, a pharisee but a sell out [as he was working for the high priest, a saducess] was tracking down the followers of THE WAY, who seem to be the dead sea scroll cult who preached a TEACHER OF RIGHTEOUSNESS [too bad 100 years older than Jesus], and the coming war of the children of light and darkness.... while in the desert he hallucinated a risen messiah who became the focus of his life after that point, as no one back then knew what an hallucination was and if he were a pagan he would surely have made a religion to whatever "god" had appeared to him...etc.
there was no fraud nor deception when he preached this new view that had litterally knocked him off his ass, so his being CON vi N c ED was very inspiring to those who wanted to be CON vi N c ED themselves. people tend to admire CON fident MEN and follow them because the want be CONfident themselves.... JWs Mormons Baptists, Muslims and others are perfect examples of people who are CON vi N c ED about their beliefs yet not one of them has see the source of their faith, only words have they accepted, yet that is enough for most of them to kill or die in the sure and certain knowledge of their CONvictions....
just like JWs have rumors and stories about marvelous and demonic occurances, peoples of the past no doubt had their own smurf stories. myth making is what the human mind does all the time and the more bizzarre a story the more emotions it can bring and the deeper the memory stains it makes and so it goes.