Why did Christianity become so popular?
Why is Jesus so popular? I mean, how did he become so incredibly well known after his death when up to that point he was a rebel and a heretic? His crucifixion is irrefutable evidence of his singular lack of popularity with the powers that be at the time. It can't be the miracle thing as he'd already performed many before they nailed him to the cross. I don't understand the contrast between his infamy during his life and global superstardom still going strong 2,000 years later.
Well, Jesus did found a successful religion, historically a good way to keep your name before the public eye. The question really is why Christianity went over so big. Considering some of the characters who've been connected with it over the past couple millennia you've got to figure the only explanation is the hand of providence. That's not an angle that lends itself to scientific inquiry, however, so let's stick to the human contribution.
Most historians give the major credit to Saul of Tarsus, better known as Paul, who converted to Christianity (although it wasn't called that yet) just a few years after the crucifixion. Paul was instrumental in taking an obscure Jewish sect, stripping away its parochial baggage, and positioning it to become a major world religion. In addition to being a tireless proselytizer, organizer, and propagandist, Paul was a creative theologian who played up the parts of Christianity with universal appeal, notably the belief in eternal life, popularly understood to mean an individual afterlife. At the Council of Jerusalem in 49 AD he also helped kibosh the idea that Christians needed to observe Jewish ritual, including (urk) circumcision, a major disincentive till then.
But it wasn't all Paul. Christianity succeeded because it showed up at the right place at the right time. The explanation usually given is that (1) the centuries-long Pax Romana that began around the time of Christ made it possible to spread ideas throughout the Mediterranean basin in a short time, (2) the old Greek and Roman pagan religions were by then completely out of gas, and (3) the imperial court was run by such a collection of cutthroats and lunatics that people were desperate for a religion promising a moral order.
All true, I guess, but none of it quite gets at the genius of the thing. There were many competing cults at the time, in particular the so-called mystery religions, that vanished with scarcely a trace. What set Christianity apart was its sophistication. It was the West's first modern religion, coupling a coherent and attractive picture of how the world worked with a commonsensical moral code. Most western religions prior to Christianity, Judaism included, were narrowly focused ethnic affairs, primarily concerned with placating a perpetually pissed-off godhead. (The Roman state religion was merely an amalgamation of such local beliefs.) Christianity, in contrast, offered the following propositions: God is good, God is universal, God wants you to live forever with him in paradise provided you … well, exactly what you had to do to be saved was a matter of dispute. But the point was, you could be saved.
Many religions previously had had some notion of an afterlife but, as in the Greek belief in Hades, it was often thought of as some sort of astral garbage can into which souls were pitched once stripped of flesh. Christianity turned this bleak idea into the positive concept of salvation and resurrection. (In the church's earliest days it was believed the second coming would occur within the lifetimes of those then living, which made acceptance of Jesus all the more urgent.)
The idea of salvation was appealing enough in its own right but it had an equally appealing subtext: the universe makes sense, you have a central place in it, and you can, up to a point, control your own fate. (I realize we get into the free will vs. predestination argument here, but you see what I'm getting at.) The complexity and emotional power of this system of belief swept away the primitive religions that preceded it. Tellingly, Christianity made less headway against the religions of the East, which offered a world view that was equally compelling.
Today a few skeptics feel Christianity itself has run out of gas, but I'm not seeing it. Assuming you're not merely going to switch to some other well-established religious tradition, or else take up with the Shirley MacLaine crowd, what else is there? Sure, I know some profess to take solace in science. But who in his final hour rejoices at the thought, onward to the void?