The Kingdom of Kongo was interested in trading with the Portuguese for a variety of reasons. Some of the reasons are:
Access to European goods: The Portuguese brought European goods such as textiles, firearms, and luxury items that were not available in Kongo. The Kongo elites were interested in acquiring these goods for their own consumption and for trading with other African groups.
Economic benefits: The Portuguese were willing to pay for Kongo's exports of ivory, copper, and slaves. This created an economic incentive for the Kongo rulers to engage in trade with the Portuguese.
Military alliance: The Kongo rulers saw the Portuguese as potential military allies against their rivals in the region. The Portuguese had superior military technology, such as firearms, and were able to assist the Kongo army in conflicts against neighboring states.
Religious conversion: The Portuguese were also interested in spreading Christianity to Kongo, and this was an opportunity for the Kongo rulers to be introduced to a new religion and to establish religious ties with Europe.
Overall, the trade relationship between the Kingdom of Kongo and the Portuguese was based on a combination of economic, political, and cultural factors that were beneficial to both sides.