Frederick Douglass is very detailed in his description of Mr. Plummer. Why?

Frederick Douglass is very detailed in his description of Mr. Plummer its because that its a memoir and treatise on the abolition written by famous orator and ex-slave, its himself. It describe the events of his life and is considered to be one of the most influential pieces of literature ti fuel the abolitionist movement on the early 19th century in the United States