I'll give you a motive. Mrs. Van Dam is a complete and total whore. Wacko neighbor becomes obsessive over it, wanting in on the action. Dances with her at bar and just can't take it any more. If he can't have her, he'll have her daughter. Goes in to house, hubby thinks its just his slut wife and her slut friends coming in to do drugs and have an orgy, so doesn't check to see who it is.
Wife comes home with friends to do drugs and have orgy, notices the alarm has been tripped, but just figures its part of the constant cycle of people coming in to do drugs and have orgies, so doesn't check on her daughter till morning.
Her lifestyle had nothing to do with it. Right.