The typical pedophile is an unbelievably manipulative person that is able to position themselves within close proximity to their targets. They often have multiple victims (like 50-100). Marrying someone to get close to their child is common as well.
It's amazing, but they fool people. I mean, Will Smith and Nicholas Cage had him teach their kids...think they'd let someone who is obviously creepy get close?
It's scary, but this is sort of a textbook case. For reference, consider the Dennis Gray case in Toledo. Very similar story--except without chess.
Careful who you leave your kids with for any amount of time.