Could it be a question of how well individuals can communicate over a distance? Fundamentalists are a minority, and without some form of publishing you'd be unlikely to meet many during your lifetime. But along comes the printing press, and suddenly any halfwit can a) get hold of a religious text, read it and make thier own interpretation, and b) publish a pamphlet with thier ideas. They could find someone a thousand miles away with the same ideas and suddenly you've got a movement going. You see a similar thing in the resurgence of Paganism - Without the internet, it would just be one weirdo* in every town, but today it's one of the fastest growing religions.
Socrates would have slipped under the radar, except he made the mistake of becoming famous - a sort of self-publishing. He should have stuck to sculpting...
(*No offence to any neo-pagans! But you are weird.)
Mat 27:5 And he went and hanged himself
Luk 10:37 Go, and do thou likewise.