What does the author owe us? Disappointed at the ending of another novel

I like a lot of aspects of Juan Gabriel Vasquez's novel Reputations - the clarity of the writing, the efficiency of the storytelling, the commitment to serious issues in particular the responsibilities of journalists - and I wish I liked the novel as a whole more but I think JGV let some of his best opportunities get away, especially in the last of the three sections. At the conclusion of the novel, the woman who was, apparently, sexually abused (by a Bogota politician) while she was a child visiting the house of political cartoonist Mallarino, returns to the scene of the crime to learn more about what actually happened to her. Mallarino has little direct knowledge of this abuse and, in fact, shares some of the responsibility because of his complete lack of supervision of 2 7-year-old children in his house during a party (a responsibility that JGV never significantly considers), but he agrees to the woman's request to track down the widow of the politician who molested her. He feels wracked w/ guilty himself, in that the day after the abuse he drew a cartoon implying that the pol was a pedophile, and a day later the pol killed himself. It's kind of amazing that he hasn't pursued this issue in the past 2 decades, but maybe it did take this visit from the victim to stir him up. Spoiler here: The 2 of them spend most of a day trying to locate the abuser's widow, and at the end they are about to confront her in her office (a travel agency, for what that's worth) and the novel ends. At the conclusion, Mallarino reflects on this life's work and wonders what had changed as a result of cartoons and he believes nothing has changed - this seems extremely doubtful, as his work is widely recognized, praised, and feared throughout Colombia, so what really causes him to doubt everything? - and he goes home, writes a resignation later to his editor, and dumps and destroys his drawings and his drawing materials. That's a huge and strange thing for him to do, and I think JGV owes us more in explaining what would lead to such a drastic outcome: proof somehow that the accused was innocent, perhaps? Regret about ever drawing that cartoon and rushing it into print (at least in the U.S., no newspaper would run such a cartoon)? JGV raises many intriguing and important issues over the course of this short novel, but in the end he seems to just shrug his shoulders and abandon the project. Too bad - it's a good novel that had potential to be much better.