One of the most surprising things in this world is whenever you learn that your once held beliefs are completely untrue. That is the kind of thing that is always hard to process. It makes sense why. We have a desire to be right at all times and it can be devastating when we are not, especially when we are wrong in a spectacular fashion.
For example, you might grow up thinking that all dogs are boys and all cats are girls and be shocked when you learn that isn't true, because how could that possibly be true?
Oh, I'm sure you knew everything growing up. Who are you to judge me?
When I was in kindergarten, there would often be an announcement over the intercom John Doe (or whoever) please come to the front office for dismissal. All I heard in dismissal was "missile", so naturally my 6-year-old self thought it was something missile-related, and I was terrified that one day I would be called in for it