Why did African rulers and traders supply slaves to Europeans?

African rulers and traders supplied slaves to Europeans primarily for economic gain, as the transatlantic slave trade provided significant financial incentives through the exchange of goods like firearms, textiles, and alcohol. Additionally, local power dynamics and rivalries often led to the capture and sale of prisoners of war or those from rival tribes. The demand for labor on European plantations in the Americas further fueled this trade, creating a profitable market for both African suppliers and European traders.