This hits the nail on the head. The problem with the DRC (Congo) is that it is basically the only viable source for certain resources on the planet. It is very easy for private entities to take control over the entire world's supply through a private military force. If there was a second country that could extract the same resources for a similar cost, the lack of stability would cause the DRC to fall behind in production which would dry up the revenue stream for the private military force.
The interesting fact about competition on the world market is that the easiest way to compete is by making the private and public sector work together. People complain about China subsidizing exports for unsustainable prices, sometimes below the cost of production, however this is only possible because the government is ensuring there is enough stability in the country for those companies to continue to exist and because the government is actively supporting these growing industries even if there is some inefficiency.
DRC basically has none of that, if anything the private sector may have an unreasonable degree of control over the government but the government has no control over the private sector.