"Things happen because the plot says they should.
All fictional realities have this underlying principle to one degree or another.
It is the reason Plot Technology and Plot Armor work. It's why the hero always succeeds where many before him have failed. It's why it seems like the world's out to get the protagonist. It's why the reasonable explanation is almost never true. Reality itself is mutable before the will of the plot.
Of course, it's always possible that amazing things don't happen to the main characters because they're the main characters, but that they're the main characters because amazing things happen to them. After all, stories tend to gravitate to remarkable figures."
Quoted from Theory of Narrative Causality