If these African countries are already making profits from resources that China assisted in developing, why does China also need to provide investments for industrialization? Couldn't these countries reinvest the profits earned from resource exports into industrialization? If they were to do so, China would be more than happy to provide the machines, tooling, technology, training, and consulting services at a fair price.
The usual reason: market access.
BYD builds factories all over the world. If a sufficiently large market imposes tariff barriers for imported cars, why wouldn't car manufacturers invest?
Another reason is access to raw materials, China transferred a lot of nickel mining and processing technology to Indonesia for access to their nickel mines. Why wouldn't China make the same agreement to Africa for a similar consideration.
China isn't going to climb up the ladder of industrialization and kick away the ladder. It has been perfectly willing to help other countries up too, for a price.
Actually I think the biggest argument against it, is Niger's greed and stupidity in stealing Chinese investments. China invested a lot of money into that country when no-one else would. What Niger did is going to make Chinese companies very wary of investing in Africa. If China investments in Africa dry up, blame those retards.