Help with Questions to Perfume: The Story Of A Murderer: After Grenouille leaves the town of Grasse

After Grenouille leaves the town of Grasse, where he has caused so much death and suffering, his case is officially closed and we’re told, “The town had forgotten it in any event, forgotten it so totally that travelers who passed through in the days that followed and casually inquired about Grasse’s infamous murderer of young maidens found not a single sane person who could give them any information” [p. 247]. Why do the townspeople react this way? Why isn’t it possible for them to integrate what has happened into their daily consciousness?