Because this evil man got his kicks from doing what he did to those who were either incapable of putting up a fight, or even telling anyone about it, or those he knew he was scaring half to death...

Which part of the paedophile/sociopathic personality don't you understand? He didn't WANT an ordinary relationship, not even one where there was no emotional connection to 'willing' girls, he wanted to be the one to hold the Power, the Fear, the Control...the SECRET.

It was the very fact that his victims were unwilling or immensely vulnerable that he got his orgasms from...

Evil Personnified.....