The reason: Almighty God Jehovaher inspected the planet in 1918 and just wanted white folks because they knew how to run dem dare printin presses.
When I was at Bethel it was mentioned that the current GB ('75) was the german mafia. Check out most of their last names. As the borg attracts more diverse people you will see less white people in positions of responsibility. There are few if any white people becoming witness vs black or hispanic.