This isn't surprising, it's inevitable.
If you folks knew how common pedophilic fantasies are amongst the general public, you would be shocked. Just look to cultures like Japan and Russia that don't strongly condemn such things, and you'll find it's about 15% of the population. It's only less in the West because of the near homicidal stigma attached to it that makes people vigorously hide that part of themselves.
Fortunately, this also shows that the vast majority of those people don't offend.
We also tend to define pedophilia as "anything sexual involving a minor", while reacting to it as if it means "violent rape of a toddler", so no shit, we sexualize youth all the time, the 18 year mark is a legal and social formality, not a hard limit on human attraction. Adults will find themselves attracted to teens, and they won't reveal that because who the fuck ever would?
If anything, the issue isn't that people have these attractions and fantasies, it is that some portion of those people can't separate fantasy from reality and are willing to hurt a child to get what they want, or they are sociopaths that consume child porn without feeling disgust for witnessing horrific child abuse.