Unconscious biases are well studied, and a good presenter can show it live on stage.
Please explain to me how %85 of Fortune 500 CEOs are white men. I don't believe for a moment that white men (myself included) are generically better at being CEOs, or at performing any of the roles that lead up to those positions.
The unconscious biases that the people in those positions choosing their successors to look like them selves is a strong explanation of this, and studies have been show that in controlled situations this sort of things happens all the time. Even by those who want things to be color-blind.