Why do so many people tend to deny the existence of African empires/kingdoms?

The Ancient and Medieval African Kingdoms: A Complete Overview

Note: Why do so many people tend to deny the existence of African empires/kingdoms?

The indoctrination starts very early in the upbringing of children.
And because of the colonization there was a great opportunity to hide and destroy a lot. Even in their Bibles and other beliefs they have falsified the ancient writings in favor of justifying their crimes of slavery. And the slave becomes a legal property of the buyer man: according to Church and State with the Bible still in their clutches ☠