And then after it's rebuilt, with schools and human rights never seen before, the military trained by the best with the best equipment, they'll fold like a cheap, suit, instantaneously, when rapists and thugs drive in with Toyotas and AKs. Everything got much much worse for the civilians.
The neocoloianialists left, and lost thousands of lives of their own, and their corporate sponsors lost their oil too I guess.
The actual method is through what China is doing with the Belt and Road initiative, what the World Bank, and what European colonial powers did in peacetime.
Get the poor country addicted to updated infrastructure and easy money, then when you need something or they want out to lessen payments as they're on more established, you pull the rug out from under them, unless they agree to some choice terms like giving you small things like minerals rights.
Edit: or They can go to the elite and offer them personal fortunes if theyd only sign off on X resource rights.