Any "race problem" SV has is largely a result of any "race problem" that exists in society at large.
For example, why are there not more black engineers? We can elaborate at length on why there's a lack of black engineers. Whatever the reason, the sequence of causality is "few black engineers => few black SV entrepreneurs"
Some people (on the right) might say there are few black engineers because blacks are dumber than other races. Others (on the left) might attribute the discrepancy to sociological factors. Regardless of how you explain the "lack of black engineers" it's this discrepancy that's causing the lack of blacks in SV. I would bet if there were as many black engineers then there would be proportionately more funded black entrepreneurs.