Unfortunately, the historical documents of the Galactica's mission were badly garbled when they were received. Gaps had to be filled in and extrapolations were made in order to present a complete narrative.
So we ended up with two interpretations of the mission of the Galactica, the fleet, the crew, and the civilian survivors. Personally, I appreciate both interpretations.... and I suspect that the truth is even further from what we have seen on TV.
(My own theory is that the Colonists were actually a race of intelligent daggits...)