Finding the genetic causation of intelligence would be fantastic.

HBD isn't the idea that there's genetic causation of intelligence, however; it's the idea that the genetic causation factors vary in frequency between population groups (namely, races), and specifically, that certain population groups have lower intelligence as a result in the variance of frequency. To which I must respond that, while it should surprise us if those genetic causation factors don't vary in frequency across population groups, it should also surprise us if the frequency distribution of given genetic factors consistently advantages or disadvantages a single population group. (That is, there should be genetic causal factors which improve intelligence that are more common in black people, as well.)

Which is to say, HBD, as a proper idea rather than racism, suggests we should be mixing races to get the best genetics from every group. Given, as I understand it, that the greatest variance in genetics tends to be in African people, the ideal is probably closer to the African cluster (being larger and thus having more potential for positive factors) than the European cluster.

But that isn't the position HBD advocates generally take, to put it mildly.