I have also seen kids who were raised in incredibly strict households go off the deep end once they escaped
we called this "Catholic School Girl Syndrome" and it was very real. These girls were seriously oppressed until they went to college and then they were free and went wild. I knew a few of them and they were some of the most "accessible" women on campus.
Brian was definitely susceptible to addiction. He was a drunk in his teens already and most of the people I knew back then rarely had anything to do with booze outside of silly parties in a field that was a twice a summer sort of thing.
I think with him it was the fact that he could do anything he wanted and never get in any sort of trouble for it aside from getting hassled by teachers and maybe a cop or two. He wasn't violent so the cops didn't really bother punishing him and he was a minor as well so there wasn't much to be done. I think in today's times child protective services would have gotten involved but it was a different time back then .
RE: The importance of parenting: Some high-school friend of mine that didn't really have guidance