I remember in 1st grade, kids talking about what Santa brought them and the money from the tooth fairy.
I was thinking "why can't all these kids see that these things don't make sense?"
But my parents never lied to me about those things, so I didn't get accustomed to holding irrational beliefs.
Yet I can't help but feel that even if they'd taught me to believe fairy tales, I still would have rejected them readily, and eventually religion the same. But who knows, I guess.
M daughter and I had a rich make believe world. As long as they harm no one and aren't used to coerce behaviour, imaginary friends can be fun. (We had a baby dragon who liked to sleep under th bathroom sink and had to be fed jujubes whenever you wanted to wash your hands.)