Corruption and poor economic management of natural and human resources are the three major reasons why well endowed countries with natural resources still remain poor. This situation is common in the Africa and Asia continents where political leadership is bereft of ideas. Nothing else explains it better. My country is an example of this. With her numerous natural resources in crude oil, bitumen, coal, gas, limestone, lead and zinc, just to mention a few, Nigeria is still categorized as a poor country. In the actual sense, the country isn't poor; it's just that it's poorly managed by her political leadership. So, it's with many other countries.
You forgot to include nepotism where one family controls one government institution. There are some government institutions that you will never here about job recruitment, they are always hidden and share among themselves when there is new applications and it will never go to outsider, it's always between the families and friends. For years now, I have never seen a single person that applied for NNPC job application openly and got the slot, always hard.
To here this becomes normal, huge numbers of people are been sideline, this is why poverty is on the increase and corruption is on the high as well. The bad impact about this is that people see it as normal, people have emulate corruption as norm in the society that it's difficult to eradicate, because tell me why should I want to stop corruption when the rest are doing it? You may even be evicted from trying to make the place better.