Whenever you hear stories of abducted women, very rarely is it someone known to them. Think of Molly Tibbetts. I honestly think that if this was personal, LE would have found them long ago. People don't keep disputes quite, other people always know. With the amount of attention put on this family not one story has come out to indicate any kind of issues. The Closs's seem like hard working, family oriented people. No indication of drug issues, criminal activity, gambling. or anything else.
To me this appears to be the act of a random stranger. A drifter maybe. A possible drug user. Maybe it's a case of mistaken identity. Unfortunately these are the hardest crimes to solve.