Writing an article from the perspective of a criminal is because it is the most convenient way to describe his psychological changes, which is also one of the highlights of the article. Psychological description is one of the characteristics of Poe's novels. He likes the themes of horror and love (as well as revenge and detective) and often exaggerates these themes through psychological description.
The article finally punished the wicked, but moral preaching was never Poe's hobby. In this article, the author wants to express an atmosphere of tension and panic, an accurate psychoanalysis with tension, and a pleasure/beauty of words.