Hurston's work was largely ignored until 1975, when an article by Alice Walker about Hurston was published in Ms. Magazine. Before this, her work had slid into obscurity for a number of reasons, cultural and political.
Dialog in Hurston's work is roughly transcribed so as to mimic the actual speech of the period, and thus it embraces the dialect and culture of Black America of the early 20th century. For example ( Amy from the opening of Jonah's Gourd Vine):
During the 1930s and 1940s when her work was published, the preminent Black American author was Richard Wright. Unlike Hurston, Wright wrote in explicitly political terms, using the struggle of Black Americans as both the setting and the motivation for his work. Because the political struggle of the time was aligned with Wright's writings, Hurston's work was ignored because it simply didn't fit in with this struggle. Other popular Black authors of the time, such as Ralph Ellison and Langston Hughes, were aligned with Wright's vision of the struggle of Black Americans, and did not sink into obscurity.
The rediscovery in the mainstream of Hurston's work has coincided with the popularity and critical acclaim of authors such as Toni Morrison and Alice Walker, whose works are centered in a Black American experience which includes but don't necessarily focus on racial struggle.