Abuse is unfortunately a generational thing. When you think about it, doesn't it make you wonder how Buck's father was treated as a child that he turned out the way he did. The strong ones break the cycle.
In Buck's book, he notes that his father was a POW in a German prison camp in World War II for over a year and in the next sentence points out that as a power lineman in Alaska, his father took a big jolt of electricity and was in the hospital for six months afterward. After Ace Brannaman did get home from the hospital, he suffered from "horrible headaches ... (that) seemed to torture him for the rest of his life" (The Faraway Horses, p. 24).
Some post-traumatic stress disorder, some undiagnosed brain damage, too much alcohol ... and there you have it, unfortunately.