[TrainedMonkey]

Confirmation bias is a thing. If you believe that magical powers are real you will find a way to explain away when it does not work while celebrating loudly when it does. For example if your wizard cannot cause rain it's because the curse is too powerful etc. Additionally growing up with something, such as when everyone around you believes something, makes it somewhat unlikely that you will question it. Finally, if everyone around you believes something there is strong pressure to do the same thing to fit in.

I have a theory that a lot of mental biases could be explained by energy minimization - changing beliefs requires brain reconfiguration which is expensive, so we tend not to do it... unless it's imperative to survival.

[Jensson]

> I have a theory that a lot of mental biases could be explained by energy minimization - changing beliefs requires brain reconfiguration which is expensive, so we tend not to do it... unless it's imperative to survival.

I am pretty sure this is a very variable trait among humans, some change their mind easily others almost never change their mind. Its expensive as you say, probably communities survive best when some change their mind easily and most keep their mind steady and only change when presented overwhelming evidence (usually from the minority that easily change).