Things were better for most blacks in 1910 than they were in 1940. Woodrow Wilson's election, and his subsequent expulsion of blacks from the civil service, started a period of decline for blacks that was deepened by the Depression, but had strongly started improving after WW II.

I'm not particularly surprised by this, actually... things also got worse after 1877 when federal troops left the South and paramilitary organizations started suppressing the black vote.

Brown vs Board of Education was a result of the change not a cause

I just meant it as a milestone that showed how things had changed, not as a specific cause of that change. The ruling would never have been made without the successful execution of a long-term strategy to gradually change legal opinions. (The first schools to be integrated by the courts were state-run law schools...)