China 'invests' in Africa where other nations don't because the Chinese government needs to get rid of wealth to prevent its own people catching up with western living standards too quickly. Once living standards are caught up, "things are getting better" is no longer a good justification for tolerating the abuses and corruption.
In 1984 Big Brother did this same thing by having perpetual war, and Chinese military spending is in fact stupendously huge, but even so they aren't actually in a war so need other ways to burn large quantities of capital. Building unprofitable railways in the middle of Africa is a great way to keep their own people poor whilst claiming some sort of moral high ground. But if these were good investments, it wouldn't be up to the PRC to make them.
In 1984 Big Brother did this same thing by having perpetual war, and Chinese military spending is in fact stupendously huge, but even so they aren't actually in a war so need other ways to burn large quantities of capital. Building unprofitable railways in the middle of Africa is a great way to keep their own people poor whilst claiming some sort of moral high ground. But if these were good investments, it wouldn't be up to the PRC to make them.