Why did africans kingdom participated in the slave trade

Because they traded and made profit from selling people from inside their dominions

The African kingdom participated in the slave trade because they were not enlighten enough to know that their people will be sold to the land where they will not be able to see them again.

They were enticed with good such as umbrella, gin etc and they will raid the neighbouring community to capture slave to be sold to the slave merchant.

Therefore they participated in the slave trade due to their level of ignorance.