List three factors that caused africa to become a growing source of slaves for the slave trade

Here are three factors that caused slavery to grow in Africa:

Slavery had existed in Africa for hundreds of years, especially in the Middle East. Europeans expanded this already existing slave trade.  

Tribal and other wars were a major cause of the growth of slavery in Africa. After these wars, the soldiers from the losing side were taken prisoner and sold into slavery.

Europeans needed cheap labor to work their land in the Americas.

i would say that the politicial parties from state to state varies.