Someone like Google should have very good information on where their current customers (and their customers) are, and that alone could be decisive.
If many of the customers in Africa are already well served by Europe (think Egypt) or the Middle East, and of the remainder a large percentage is in South Africa itself, then South Africa makes a good choice for the first.
After all, starting in SA doesn't prevent them opening further datacenter in other countries as they grow.
I didn't downvote, but honestly just don't understand your comment. I thought it was obvious but maybe I shouldn't have left it unsaid: South Africa has significantly better infrastructure than any other country in southern Africa. We're not talking a small difference. If you want to open a cloud region in southern Africa, I don't think you have any other choices.
If many of the customers in Africa are already well served by Europe (think Egypt) or the Middle East, and of the remainder a large percentage is in South Africa itself, then South Africa makes a good choice for the first.
After all, starting in SA doesn't prevent them opening further datacenter in other countries as they grow.