16. "I was told that the book explained it" In response to In response to 15
That was the effect that It/Pennywise had over Derry. Not only did it make people more violent and aggressive, but it made the adults in general oblivious to the horrible stuff going on.
In which case it doesn't really make sense that Michael isn't also oblivious as an adult. But I'm guessing the book explains that too?
Not excusing it. In fact it probably means that the movies were faithful to a fault. To truly explain it all the movies probably would've had to be like four hours each.