I’d say it’s too soon to see if China will take an imperialist approach. The US and Europe seem to be decoupling from them, so they are in desperate need of well-developed markets that will buy their products. It’s in their own best interest that African nations develop quickly (which also hurts the US and Europe, making it harder to get cheap raw materials, thus doubly good for China).
You’re right. At the end of the day, there are many factors pushing people to act, not just greed and rationality. Thank you for your reasoning and the interesting thought experiment.