Question

why did sympathies for the communist party increase among African Americans during the 1930's?

Answer 1

You might check out the book The Cry Was Unity: Communists and African Americans 1917-1936. Here's a link to the overview: http://www.upress.state.ms.us/books/259

"The Communist Party was the only political movement on the left in the late 1920s and 1930s to place racial justice and equality at the top of its agenda and to seek, and ultimately win, sympathy among African Americans."