All civilizations fail eventually. The "barbarians at the gate" who bring down Civilization A are the revered ancestors of Civilization B.
What baffles me about conspiracy theories in general: If *I* were plotting with a group of people, I would not leave secret handshakes and mysterious critters and coded messages lying around in plain sight for the edification of the general population. No one would have a clue we even existed
until we had already won. 