Why were Kinshasa and Brazzaville founded near Malebo Pool?

Kinshasa and Brazzaville were founded on opposite banks of Malebo Pool because the pool serves as the critical point of departure for inland navigation on the Congo River.1

While the Congo River provides an extensive network of navigable waterways, its lower course is obstructed by a series of 32 cataracts, including Inga Falls, which render the river unnavigable between the seaport of Matadi and Malebo Pool. Consequently, the pool acts as the downstream terminus for river traffic coming from the interior, making it a vital hub for trade and communication. The capitals were established at this strategic location to manage the transition between inland river transport and the routes leading to the coast.12