Everyone I know in DC is Military, works directly for the Govt, or works in consulting on govt. contracts. Not saying this is everyone of course, but I would assume majority of the people making over 50k work for something tied to the govt.
And that's somewhat true, especially with the contracts, but it's D.C, so that's expected.
I do know of(and personally) plenty African and Black American business owners, who have nothing to do with the gov, or gov contracts, some that employs 50 plus employees in all sorts of fields.
There's a set amount of available gov jobs, not everyone can work it.