It gets misty going back that far, talking about Kobol, but basically the Jealous God caused a war, and the war led to the Exodus of the Thirteen Tribes. The final tribe were, in some fashion, Cylons. Incarnations of immortality, they used synthetic bodies for human souls. (The truth is that we have no more idea of the level of technology at play on Kobol than we do about whether the Egyptians had spaceships, not really.) But the Twelve Tribes went to a star system with twelve planets and started the Twelve Colonies, and the Thirteenth Colony went to Earth, and life went on, for maybe thousands of years. The Colonies fought and allied and backstabbed and generally acted like the European states for thousands of years, and built robots for their warriors and labor; Earth did the same.
Five scientists on Earth, descended from the Cylons of the Thirteenth, came together to reinvent resurrection, and create synthetic bodies like in the olden times, pushed and shoved and manipulated to do so by angels. When Earth's robots rebelled and blew everything to hell -- just like the Colonial ones did fifty years ago -- these five scientists downloaded themselves into bodies on a wondrous ship off-planet, the Colony, and set out to the Colonies to warn us not to make the same mistakes.
They traveled back along the route the Thirteenth Tribe took, including stopping off at a temple the tribe had built along the way -- the Temple of Hopes. At some point they became monotheist, listening to those little angels and learning about faith from our Centurions. Not sure about the timeline there, but I do know that in the Sacred Scrolls of Pythia, the Temple of Hopes was called the Temple of Five, and believed dedicated to five priests who worshiped the One whose name cannot be spoken." That seems like an imprecise mythological gloss to me, but we will see. Pythia is like the ultimate unreliable narrator if you're looking for facts, but then, that's not how oracles ever work. Confusing the layers, imminent to historical to legendary to mythic, is a good way to end up with a Laura Roslin, or talking about intelligent design: a good way to miss the point entirely and rape religion of what little use it provides.
Of course, by the time they finally got to the Colonies -- around fifty years ago -- things had gone impressively to shit. Our robots, attempting to resolve a basic binary problem we'll talk about later, had come up with the OTG on their own, and started a war on their creators. Part of this war, because every war has an ontological component that is either about becoming the enemy or not becoming the enemy, was the pilot program of the Guardians to create human forms for themselves. This is where the Hybrids came from; even after it was abandoned, they kept going. The Earthling scientists -- the Final Five members of the Thirteenth Tribe -- in attempting to halt the destruction of the other Twelve Colonies, struck a deal with the Centurions: human bodies for peace. That's the moment of the Armistice, when Husker saw the Guardian ship take off forever. It worked.