Isn't it a bit a matter of culture, though? Colonial administrations are built to extract wealth from a country. So, when you get independence, that's still what the government, hell, even the infrastructure, is built for. Half the rail lines go straight to a port, all the bureaucrats know is how to squeeze people. So you end up with 'bad governance', even decades later, because that's the culture of governance that gets passed on, generation to generation.