You're right.
Explains why those with depressions from, say, bullying tend to practice shooting in schools.
The depression is correlated to seclusion and withdrawal which can lead to violent revenge fantasies and murderous impulses which lead to shooting in schools. It is a correlation, but the depression,
while being at the root of the violence, did not directly cause the violence.
But if we're being genuine, it's splitting hairs. An argument for the sake of argument. Absent the depression, perhaps the individual then has a better balanced emotional state and none of the after-effects materialize and violence never occurs. But there are also plenty of violent people who go through all this without depression.
My feelings on this chapter is less redemption arc and more internal monologue and exposition. Explaining his mental pathway from depression of losing his career, to his wife, to his followup job, the ensuing isolation and regret, and then ultimately venting his frustrations on someone vulnerable and not in a place to defend themselves. It doesn't feel hamhanded or overly simplified to me. The author just doesn't have endless chapters to burn on the fall of a once pro baseball player. He'll get what's coming to him.