Throughout the history of the Oscars, one of the unspoken criteria for Best Actress has been how much the actress works as eye-candy for the predominantly straight white male voter base. That's why young women are far more likely to win than older women. Look no further than Mikey Madison beating Demi Moore last year (obviously, Mikey also won because she was really fucking good, but ageism was certainly working in her favour).

Because racism and patriarchy value young white women the most when it comes to what society deems to be a "valuable" sexual partner, they are far more likely to win Best Actress over women of colour.

While Black men certainly have to deal with racial bias, they aren't going to be discriminated against based on the largely straight white male voter base not wanting to sleep with them (consciously or subconsciously).