Most of Dota players are from Europe, Americas and Asia so those places are much more likely to have pros. How many players have you seen that are playing from Africa? Black people are minorities in western countries so they are even less likely to go pro. I can name Spawn from csgo and Aphromoo from league from the top of my head.
As for me, I'm black and I dont think I stood a chance to become pro because I started playing dota at age 16-17 and hit 5k at 19 sacrificing a lot of things irl, it was a good progress but there were people like zai, rtz, sumail and miracle who were the same age as me and they have been playing hon/dota allstars since forever and they were already pros. What chance did I have? Im lucky that I became bored of dota because now I can focus on my education more.