You may also be ignoring the impact of immigration policy: there are a limited number of ways for Nigerians to (legally) get into the US - they no longer qualify for the DV program (unlike other immigrants who do not have a similar selection pressure). If you filter for educated Nigerians by leaving only F/M visa as a way to get into the country, you get mostly Nigerians who value education who qualified for the respective visa's (and their offspring) - there is nothing inherent to Nigerian culture there.
> The data showed 27 percent of non-Hispanic white Americans have bachelor’s degrees and 8 percent hold master’s degrees, according to the 2015 census. The survey also revealed that 4 percent of Nigerians in the U.S. have doctorates, compared to 1 percent of white Americans. And Nigerian-Americans’ education achievements top those of any other U.S. immigrant group. Asians come closest, with 12 percent holding master’s degrees and 3 percent having doctorates.
This article and it's viewpoint on the culture matches what my friends who are either Nigerian or have lived in Nigeria tell me. I believe it's also one of the main reasons that Jews have been able to do so well financially as a minority despite a long history of oppression -- education helps free you from being a victim to the dominate modes of sidelining a given group (I am Jewish and this certainly has been a big factor in both my family's values and others that I know, and has allowed my own family to escape poverty in Russia).
[1] https://www.ozy.com/around-the-world/why-nigerian-americans-...
Proving my theory wrong would require showing a country that is subject to the same policy, but somehow not supplying educated immigrants. If "Asia" here includes the Indian subcontinent, then I believe the article bolsters my point.
The only other country I'm aware of, that is subject to the same immigration policy is India; while I do not have the stats on hand, my gut is that Indian immigrants have higher than average incomes, are generally more educated, and/or are biased to careers in technology since that industry makes heavy use of one of the more reliable immigration paths remaining to them - the H1-B.
Random immigrants (from anywhere on earth) outperform born-Americans on income and entrepreneurship - regardless of their prior education (you can chalk this to self-selection and/or motivation). Putting in an additional filter on higher education just skews the bias further