Amazon cares a little about physical location and a lot about network bandwidth for this stuff.
So, they are building a location in South Africa that will cover southern Africa, but their locations in Brazil and Europe actually have good coverage for Africa already and only recently has the demand approached the point to be worth the investment.
The reason for the is under sea Cables provided most of Africa’s backhaul capacity, which relates a little or geography and a lot of economic development.
“Demand” and physical infrastructure have a lot to do with GDP. By Demand I mean the price quality curve people / companies are willing to pay.
Russia has 1/12 US GDP spread over a huge area. They have fairly good network capacity but simply don’t pay for that many servers. Tiny counties with good networks may randomly be chosen, but the odds are low. Where both US and China have the demand to support multiple AWS zones,