not all of them(all country in africa) are so advanced and are confortable to use technology device, this is true for the sud africa, nor africa on the other hand is getting better, and they have nothing to envy to europe or usa(i have friend that live there, so i know a bit about it)
Some 90% of the Africans live in poverty. But at the same time, there is a large community of the African nouveau riche, comprising of businessmen and migrants who have found jobs in the EU and North America. There are tens, if not hundreds of millions of people who use smartphones in the African continent. It will be foolish to ignore this large group.
90% where are you getting these stats from. Not even close according to this
http://www.our-africa.org/povertyI don't think they can leapfrog traditional banking. If they can't access the banking, how can they buy or cash out bitcoin through the exchanges, which accept fiat money deposits for them to trade or transfer fiat money to your bank account for withdrawal?
You don't need exchanges. You could have remittances coming in and then bitcoin circulating through the sale of goods and services
People are going to need a place to exchange coins for cash. They're not just going to want to barter for food or goods.