The primary customers would be electricity utilities in the region. Most of them are technically it really bankrupt and wouldn't give the lenders any comfort they'd be able to pay for the electricity they would buy over the years.
At one point there was an initiative called Westcor for five utilities (from DRC, Angola, Namibia, Botswana and South Africa if memory serves, which it might not) to build DC transmission lines through a Western Corridor (hence the name) to bring Inga electrons to those utilities. It didn't succeed for reasons I won't go into here, but in part because the proponents didn't follow the basics of infrastructure project finance. A real pity - in many ways it was a good idea.
could be a case of Dutch Disease too.