There's a video of a single Chinese guy whipping a single Kenyan guy who worked for the single Chinese guy's privately-owned restaurant in Kenya, for which the Chinese guy was fined KSh 3 million for. The same guy who had two other employees without work permits. Not exactly a good generalization of "Chinese" rather than just "shitty guy in general", nevermind of "China" as a country... And frankly it's a rather racist generalization.

China's Belt and Road aims primarily to build out infrastructure of developing countries so that their economy expands and they can buy more Chinese goods. Infrastructure is incredibly profitable, in general (each dollar spent on transportation is estimated to return something like four dollars in government returns). If infrastructure costs go down, returns go up: would you rather spend $10 billion on two dams or $20 billion on one dam and "oh look you ran out of money to build the second dam and your first dam is breaking because you didn't have experience and oh no you don't know how to fix it because you've never run into this problem before." That's the primary sell behind the Belt and Road: they're cheaper, they're less likely to fuck up, and if they fuck up China can audit the problem and fix it. You shouldn't be restricted in what infrastructure you can build by what you domestically have the capability for, because building domestic capability is extremely expensive and extremely time-consuming (and, well, let's just say that developing countries aren't called "developing" because they're swimming in money).

China doesn't profit off of exploiting resources extraction as much as it does off of manufacturing products. China's spent a lot of effort to make sure it's domestic supply chains are robust, but they're running out of room to export to the West. They have a strong incentive to make developing countries have stronger economies so they can buy more Chinese goods to grow China's economy. It's simple economics.