Final answer:
African kingdoms started capturing and selling slaves to Europeans for money, with European demand and trade goods playing a significant role.
Step-by-step explanation:
The main reason why African kingdoms started capturing and selling slaves to Europeans was for money. African kingdoms realized that they could profit from selling slaves to European traders. Europeans offered various trade goods, including firearms, in exchange for enslaved Africans. However, it is important to note that while European demand played a role, African kingdoms were not entirely passive in this system, as they actively participated in the slave trade.
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