To be quite blunt, that's due to "dry" sex and the fact that men have relations with a lot of women in addition to their wives. Not sure why you think that gays are the primary vector of transmission there.
I don't agree.
From what little I know about HIV transmission, it is very easy for males to pass it to other males and to other females. Very difficult for females to pass it to males, and almost impossible for females to pass it to other females.
Adding that up with the the African infection rate, I get that there is a lot more male-to-male contact going on there than we know about.
In any event, it is the result of choices they are making. It's not like they don't know.
I could give them a sex-ed lecture in less than an hour. It wouldn't take a five billion dollar grant. A couple million would cover it all, including travel.
I would also add that they should not bring babies into this world until they are prepared to care of them.