Why were tropical rainforest societies in the Congo less centralized than savanna kingdoms?

In the region of the Democratic Republic of the Congo, the development of centralized states was significantly influenced by ecological conditions. While the southern savanna region fostered the growth of elaborate political institutions—such as the Kongo kingdom and the Luba-Lunda states—the tropical rainforest presented formidable obstacles to similar state formation.12

Societies within the rainforest were typically organized into small-scale village communities rather than centralized states. The dominant mode of organization in these areas consisted of corporate groups that combined social and economic functions among small numbers of people. Exchange in these communities was primarily conducted through trade and gift-giving, which fostered cultural homogeneity over time but did not lead to the centralized political structures seen in the savanna.12

In contrast, the savanna kingdoms utilized symbolic kingship and military force to project power from a capital to outlying areas. This allowed them to act in a more concerted manner than the segmented, village-based societies of the rainforest, which remained decentralized.12