The summary of this is that rich country figured out low hanging and easy fruits of services(for them that is, as if it was easy for others they could not hope to sell such services.) they could provide for a fortune and use those proceeds from those services to chase after high hanging fruits of services they could deliver to the world as those one's usually require intense capital.
Poor countries therefore either have not figured out services they could provide for the world or they have figured it out but are not investing the proceeds from it in the infrastructure and well-being of their country, being a Nigerian I would say most poor African countries are poor not because of the former but the later due to corruption,tribalism,e.t.c.