The 1920s were a time of "unprecedented" opportunity for African Americans. Not that "discrimination" against them would stop for a long time to come. But at least this stopped "expanding," and began to see a pullback.
Following the immediate "euphoric" period after the Civil War, there had been an anti-black backlash that had resulted in increasing restrictions on them for over 50 years. Immediately after the war, a number of southern states passed "black codes" that forced former slaves to work,and pushed them into a form of slavery. The Ku klux Klan
was organized in the late 1860s to further hobble African Americans. After the end of Recontruction in 1877, this was followed by Jim Crow Laws in the 1880s and 1890s, that mandated segregation, and were ratified by the Plessey v. Ferguson Supreme Court decision in 1896.
The 1920s saw a modest lessening of these pressures. The First World War had created a shortage of white workers by reducing immigration, allowing blacks to get factory jobs in the North for the first time. This led to the "Great Migration" of blacks to the North, where they faced real, but lesser discrimination than in the south. There as a large concentration of the in Harlem, New York, and they created a Harlem Renaissance that made black culture a force in American society. For instance, Black writers and composers and white publishers mingled freely for the first time. Harlem also had an international impact, pulling in Caribbean and French Africans from abroad. All this helped create a "New Negro" that was more acceptable to both blacks and whites than the old one.
The 1920s were a time of relative social freedom, for non-Establishment groups in America such as women and minorities, particularly blacks, that would not be seen again until the 1960s. It was also a "fun" time, and the African-Americans got a share (perhaps not their "fair share") of it, unlike earlier times.