Lee and Adama as well as Kara and Roslin have made this prophecied haven their strategic goal and they've fought and died in the race to get there and to interpret the mystical clues along the way from Pythia/Eye of Jupiter/the god or gods, etc.

You're right, of course. But at first, Earth was not really their destination. It was a ploy to keep the morale up while they figure out what to do exaclty. Later, Roslin started to bring the mysticism into play but even she used it as a political way to grant support. The big turning point came when they found Kobol and the Tomb of Athena. But even there there was enough physical evidence that there was some truth to the old myths to support believing in them as something real. And to take the more mystical aspects (as the vision or whatever they experienced in the tomb) with a grain of salt - something that is accepted though it can't be explained. Bill and Lee are more worried about the physical clues they found along the way than in the prophecies themselves. When Kara's destiny became something bigger than life there wasn't really anything concrete to base it on. It was purely mystical and it didn't make a lot of sense.