France has many other investment options with much better expected returns, especially once you account for the cost of maintaining a military presence. There is much to criticize about recent French policy in Africa, but charges that the French government is cynically enriching itself by exploiting these countries just don't match observable reality; talking with people who have spent time working there will quickly confirm. Additional evidence comes from China's attempts to enrich itself in Africa, which have mostly failed to produce the desired riches in the expected amounts.