Let's put this in terms that make more sense for the vast majority of us. Let's envision your average chain restaurant. Hiring a RB is like hiring a server or greeter. There are tons of qualified candidates and a line of people to replace them if something doesn't work out. These are low risk decisions so often bias doesn't come into play when hiring. Just pick someone and let them give it a go. If they do good great, if they don't, then drop them.
Hiring a head coach is like hiring the CEO. To get to CEO there are many steps along the way. You have to start way down the chain (maybe even as a RB or waiter). There is networking, relationships, performance, etc, etc, etc. You have to make the right step almost every decision you make for years. And then when you get to the threshold of becoming a CEO you still don't have any experience actually being a CEO so the people doing the hiring still have a lot of uncertainty.
Now think about all the places along that journey where bias can come into play. I think it would be assinine to assume that this climb is just as easy for a black guy as it is for a white guy. Think about my EKY example. You think people from. EKY haven't been looked over for management jobs because someone didn't like their accent? Of course they have. Is that fair? Of course not. Black people have a double deck stacked against them. People don't like their accents, people don't like the way they dress, people don't like their skin color, people think unsafe when they're around, etc, etc, etc.