I believe personally that it was about the end that was about to come for Jerusalem which came around 70AD. Jesus had the right idea and he noticed that the way the Jews were going would not be tolerated much longer by the Romans and the Romans had the nasty habit of punishing any uprisings by burning down the whole city. His prophecies were sufficiently vague and Nostradamus-like to be interpreted several ways. After that it kinda tapered off and split up into several sects and philosophies (a huge problem by the time John wrote Revelations) that eventually developed into some of the religions we know today.