I think that what we fail to realize in all of these unfortunate situations is that these are 18/19 year old boys who have not been fully prepared to handle the sudden attention, fame or life changing money that has come their way. It is normal for teens to think that nothing bad could happen to them, they still do stupid kid things once in a while, still experience peer pressure, why would sudden fame and fortune change that?
It takes a very smart parent to be able to watch carefully for signs that things may be getting out of control. Unfortunetly, lots of parents are also caught up in what is happening and lose sight of what really is important.
They naturally expect that their teen is going to suddenly not do things kids their age do because they may be famous some day. Not so.