Because the human brain doesn’t intuitively count the way we’re taught in school.
Our brains are very good at understanding 1, 2, sometimes 3 and, “many”. That’s the data we get from smart chips, young children and isolated pre-literate societies.
Counting bigger numbers requires abstract systems. Our brains can do that but it’s much harder and we don’t grasp it as well.
The practical offshot of this is that while it’s intuitively obvious that a small space like a garage will quickly fill up with toxic gasses, it’s far less intuitive that a “very big” outside can get saturated by a “pretty big number” of cars.
Africa has a number of factors in its favor that make it a potential economic powerhouse. It has some of the largest natural resource reserves in the world, it has a huge population, it’s conveniently located on or near several important trade routes.
It’s also cursed with some pretty bad natural infrastructure. The rivers in Africa don’t provide good access between the center of the continent and the coasts.
China had about the same GDP a Sub-Saharan Africa in the early 1990’s https://data.worldbank.org/indicator/NY.GDP.MKTP.CD?end=1996&locations=CN-ZG&most_recent_value_desc=true&start=1960 It’s taken China 35 years to get from there to it’s current spot as 2nd largest economy in the world. And that was for an economy that was growing at nearly 2x the rate of the rest of the world for most of that period. https://data.worldbank.org/indicator/NY.GDP.MKTP.KD.ZG?locations=CN-1W
That’s not to say that Africa can’t become an economic powerhouse but it will take a lot of work and time. It would take sustained investment and reinvestment in Africa over several decades.