Agree 101% with nossond
Hope the following does not offend anyone’s sensibilities
You are telling me that he grew up in a normal home and now he has gone haywire. That he grew up in a normal home implies that he is normal, if so, why has he gone haywire?
A possible suggestion is that every person in every stage of their lives knows what they are working towards and has an image in their mind of what they want to be, soldier, sailor, tinker, married, single, wealthy, poor, rosh yeshiva etc.
The above is why kids – go to university, hang out with friends with similar lifeplans, etc., birds of a feather flock together.
If it is not possible to comprehend what he is doing it sounds like it may actually be incompregensible, i.e. he has no inner logical plan of where his life is heading