It's not as if most people are rich in Equatorial Guinea. It's an appalling outlier in terms of inequality, even on such an unequal continent as Africa.

"Only about half of the country’s population has access to clean drinking water, overcrowded living condition is—surprisingly given the country’s low population density—rampant and very few children enjoy the advantages of urban life such as education, medical services and recreational facilities." https://borgenproject.org/equatorial-guinea-poverty/

I tried to find data about GINI for the country but the World Bank and the UN don't have anything. http://hdr.undp.org/en/content/income-gini-coefficient