The real answer wrote:
Morocco is similar in climate. Both have high altitude regions.
Really, it's because the African countries that do well have copious doping access, connections and knowledge, while countries like Egypt do not. There's dozens of other African countries that also haven't won anything in running. If somebody was willing to start trafficking EPO and steroids into Egypt for runners, they would start winning just the same.
This is indeed the real answer.
The old poster SubwaySurfersAddiction used to refer to it as the EPO triangle : Morocco - Spain - Italy.