Most people can drink without getting drunk, or ending up becoming alcoholics. It's different for some people for psycho-social and biological reasons.

A high percentage of people with bipolar disorder will face drug and/or alcohol addiction at some point in their lifetime.
Please read this article:

Bipolar Disorder and Addiction | Dual Diagnosis

I think it's really nice that you can look back at your father's drinking behavior with some compassion now.