You overlook a number of high profile African Americans (Tony Prophet and Robert F. Smith for example) in tech and Silicon Valley and highlight a number of Africans (Nigerians in particular). Is your criticism also addressing the lack of Africans in Silicon Valley as well?
Statistically, the American immigrant population from Africa (around 2 million people) seems to have a very different background from most American born African Americans (around 40 million people).
Overall, African immigrants (like many other immigrant groups) tend to have very high education/economic mobility, due to the selection effect - if you don't have those characteristics, it's hard to immigrate to the US.
But if you lump both groups together as "black", the likely result is that tech companies trying to make up for lack of representation in American born African Americans, will end up filling most of the gap with African immigrants, because immigrants are more likely to have the background tech companies are looking for.
Which is great for immigrants, but does it end up helping African Americans?