When there was no flood, no spaceship, no death and destruction, the cult members were faced with two possible "facts." Option No. 1: They were wrong to believe. Option No. 2: They were right to believe, because their faith stopped the flood.
In fact, for the most sincere believers, option No. 1 probably didn't enter the picture. And if it did, they probably would have immediately forgotten it.
Confirmation bias can explain everything from unbudging stereotypes to increasing political polarization. The theory goes: We are more likely to believe (or seek or remember or even notice) the "facts" that support our current viewpoints, and less likely to believe the ones that would require mental adjustment. The more deeply ingrained or self-defining or consequential the current viewpoint, the further the mind might go to ignore the new evidence that would disprove it [source: Arnold]. Attempts to debunk an irrational belief will tend instead to reinforce it, as the believer may have come to see his or her perseverance as heroic, as standing up to the "establishment" [source: Arnold].
While belief perseverance is not limited to the realm of science, when that new, threatening evidence takes the form of overwhelming scientific data, there are some approaches that work particularly well to keep the conflict at bay.