Why is Richard Wright so detailed in his discussion of the lynching?

In "Big Boy Leaves Home," Richard Wright provides details about the lynching of an African American teenager. The details are graphically stark, and it is a daunting literary experience for the reader. It is very likely that Wright provided all those details to highlight the oppression endured by African Americans during the Jim Crow era.
The details describe the terror, excruciating pain, and degradation endured by victims. The NAACP notes that 4,743 lynchings occurred between 1882 and 1968 in the United States. Of those lynched, 72.7% were African Americans. Most lynchings occurred in the South.
In Wright's story, four African American teenagers (Bobo, Big Boy, Lester, and Buck) secretly take dips at a swimming hole on private property. The boys enjoy themselves until a white woman shows up. Upon seeing the woman, the boys panic and frantically try to get their clothes on. Meanwhile, the white woman screams for her husband.
The husband shows up with a rifle and fatally shoots Lester and Buck. Just as he is aiming at Bobo, however, Big Boy lunges at him. In the struggle, Big Boy fatally shoots the white man. Knowing that they are in danger of being lynched, Big Boy and Bobo make a run for it.
As the story progresses, we learn that Big Boy just manages to get away. However, unlucky Bobo is caught and made to suffer an excruciating death. During the lynching, individuals gleefully proclaim that they have appropriated one or more of Bobo's body parts. It was a common practice to take body parts as souvenirs during a Jim Crow-era lynching.
So, Wright's details were meant to highlight the depth of suffering endured by African Americans during a dark era in American history.
https://www.pbs.org/wgbh/americanexperience/features/emmett-lynching-america/