The way I understood it, their deaths were foretold. They were destined to die - they saw it in their visions and believed it. They didn’t have a choice but to die.

Their deaths were not the reason for the disasters, the family’s failure to choose was the reason for the disasters.

The only way to save them and the rest of the world was for the family to make their choice.

What I found inconsistent was that we were told the family had to choose together, but in the end it was more like one of them made a sacrifice against the will of the others.