A fifteen year old is immature and set on proving how mature they are. An insecure one might be drawn particularly to an older attentive male.
Later she would be horrified when she realized she was manipulated and used by a married man who had kids her age. She would be concerned for his family and how he might be manipulating other young girls. She might well be in a real relationship and trying to deal with her actions towards his wife as she is contemplating marriage herself.
He is damn lucky his wife is forgiving, but he is paying a price for breaking civilizations rules. Morality has always been about protecting the integrity of the essential social unit, the family. Property value of women may have figured into it but adultery is the higher sin than fornication in every religion that I'm aware of for both genders. Now he was both morally and legally in the wrong and he will pay for it. There are reasons for laws about age of consent and he has 2years to think on it.
I wonder when he confessed to elders. They are standing by him. Maybe he is an elder, because a regular JW who doesn't promptly confess is usually judged unrepentant and DFd. Remember their video with the young guy who impregnated his bar hook up? Doesn't an elder get a free pass after 3 years?
I wonder what's happening to the girl in the org. I wonder if she confessed to elders and they urged her to report? I know th wtbts will be changing. I wonder if this is a start?