Wealth can't be created by transfer payments, it can only be grown.
Many countries, like Zambia, are really bad at economic growth. The reasons can be kleptocracy, bad legal systems, but also lack of investments in infrastructure.
This is really the major issue. "Growth" in the sense of "increase in actual production" is going terrific (granted, mostly by virtue of "Copper is practically the new oil - reserves, especially easy to access them" matters). What isn't going so great is the second part of "We should be careful with that and funnel it back into the national economy. Pay to play - the copper and other metals are only there once and we know what they are worth".
You can't really grow forever, but you can still grow and they do. But this is sort of like the early oil rush in the midwest. Oh wow, holy crap, people will give us 25 cents a barrel for crude! And we don't even have to dig it up, they'll even come over and do it! How cool is that?!? Uhh, not that cool when you were sitting on top of oil reserves the size of saudi arabia that are now all but bone dry with some entrepreneurial farmers pumping up a few barrels for a slight short term profit.
The main law that seems to be missing everywhere is "X amount stays here. No really. Invest whatever you want, but a certain part of the gained value is stuck in the local economy and another chunk is paid to locals because OUR HOUSE".
Zambia has been growing at 6+ % for 6-7 years, raised a massively oversubscribed bond issuance to invest in infrastructure, and a Transparency International corruption perception index score just shy of Italy's.
All of the things you mention are relevant, but things are changing more quickly than you would expect.
Many countries, like Zambia, are really bad at economic growth. The reasons can be kleptocracy, bad legal systems, but also lack of investments in infrastructure.