Which culture developed in East Africa as a result of the region's involvement in overseas trade?

The answer is: Swahili

The development of Swahili culture occurs on the coastal region in east Africa. Due to its close proximity with the sea, international trades often choose this territory as their ship destination when they wanted to conduct trade with people in Africa.

As a result, cultural assimilation occurs between the traders and the local people, creating the Swahili culture that we know today.