Kate Gold asked herself how those tree tomatoes got to Kenya from the Andes, and then answered her own question:
“missionaries or settlers moving north from the Cape of Good Hope after the Boer Wars may have taken seeds of C. betacea with them to Kenya and Tanzania.”
Seeds had come to the Cape from the Botanical Gardens in Jamaica. How tree tomato reached Jamaica is not clear, but it was well established there by 1884 (but, interestingly, is seldom seen there today).
Lots more information and a map showing dispersal routes around the world:
Bohs, L (1989) Ethnobotany of the Genus Cyphomandra (Solanaceae). Economic Botany, 43(2), 1989, pp. 143-163
Sort of like Physalis, then?