My theory on why no black actors were nominated? None of them hit the money shot. Now I know that's a term most associated with the porn industry, but most non-porn films would not succeed without their version. The money shot for an actor takes a good performance and seers it into your heart. Let me give you some examples: Denzel Washington won his first Oscar for a film called "Glory." His performance was outstanding, but his money shot came when, while being whipped, a single tear ran down his cheek. I saw that movie with a theater filled with white people and that one moment broke everyone's heart. Cloris Leachman's money shot came with a coffee pot in "The Last Picture Show." Forrest Gump sat down with his 4 year old son in front of a TV. Matt Damon might win the Oscar this year because his money shot came towards the end of The Martian when he's strapped into a seat and the camera zoomed in for a closeup. The money shot comes when you change places with the actor and you feel his joy, or fear, or pain.
And, as in porn, the money shots don't last long, but they are essential if you want to snag an Oscar nomination and possibly an Oscar. These people are actors, good performances are a dime a dozen, they have to be if a film is going to succeed. The Oscar voters will never be politically correct, they will never nominate someone simply because of the color of their skin. If you want to get their vote you need to do more then just perform, you need to give them, and the audience, that money shot.