via Political Islam.
The story of slavery that we are told never includes the role of Islam. The slaves were captured by jihadists and brought to the coast. We have a detailed record of how this took place. Prosperous regions of Africa were destroyed by the Arab slave traders. Out of the slaves that were captured, only 20% of them ever made to the pens on the coast to be sold.
There is an oddity in the language used in historical record — Arab, not Muslim. Their religion, not Islam. Raid, not jihad.
We will never understand the slave trade until we understand the Islamic slavery.