They are dying of hunger because of corporate greed. Africa has many of the world’s most resource-rich areas, but they don’t realize the profits: Western corporations that extract the resources using local slave labor do.
"Corporate greed" is a fun slogan, but means nothing in reality. In the few areas where the government is exploiting its own natural resources (instead of outsiders), the working and living conditions are not inherently better. If it worked that way, all of the middle east and large areas of Africa wouldn't be so destitute.
Control of the resources or territory wasn’t magically delivered to the people with equity. The colonial infrastructure of control was turned over to local friendly interests and their successors. (Through revolutions, coups, etc)
Handwavy, vague "post-colonial" whatever isn't a reason, it's an excuse.
Plus, if there’s a popular revolt, they are usually motivated by religious, ethnic or ideological factors. Status quo is the interest of the big powers. That tends to bring direct or advisory intervention by western military forces.
I’d suggest spending a few minutes googling, you’ll learn alot.
These are as a category unstable political situations and it is vanishingly few who manage to develop their way out of it. More common is descent into further chaos, with major powers standing by to ensure that it does not disrupt resource extraction.