I'm just struck by how the issue of guilt here turns on mental processes inside someone's mind and not at all on what actually happened in physical reality.

Mental processes inside someone's mind actually happen in physical reality.

Just kidding; I know that's not what you mean. My actual reply is that it seems manifestly obvious that a person in some set of circumstances that demand action can make decisions that careful and deliberate consideration would judge to be the best, or close to the best, possible in prior expectation under those circumstances, and yet the final outcome could be terrible. Conversely, that person might make decisions that that careful and deliberate consideration would judge to be terrible and foolish in prior expectation, and yet through uncontrollable happenstance the final outcome could be tolerable.