I wonder if he did it in order to get back at his ex.
The only thing she did wrong, that we know about, is trust him with their daughter. Divorcing him certainly wasn't the wrong thing to do.
I know plenty of women who'd say that if their loving hubby raped their little 14-year-old sister, he'd have gotten off pretty easy if all they did was divorce him and send him up the river for nine years. Down close to the Gulf Coast where I live, this guy would've long since been a scattered collection of fish turds.