WE made them rich in buying their oil.
Not only that, we found their oil for them. In the 1950's and before these countries were dirt poor. The tallest buildings were 2 story clay huts with no electricity or plumbing. We, meaning westerners, found the oil for them, gave them the technology to pump it out, and then bought that oil. It's been that way since the 50's-60's. If it wasn't for westerners they'd still be diving for pearls living on a dollar or two a day instead of building 5 star hotels and indoor ski resorts in the middle of the desert.
Oh and why have the oh so smart Chinese to steal the knowledge and the achievements of the messy West if they are sooooo successful
Because it's more practical and smarter to simply steal it and reverse engineer it for their specific purposes. It's like if you have the option to study for a month for a difficult exam or can get the answers from a student who took the class last semester, or design an airplane from scratch and spend millions upon millions on R&D and testing or simply copy a proven design, well most would chose the latter.
Apropos debts, what will China do once we all stop paying?@ Bratwurst Boy
Then they'll start taking ports, infrastructure, etc. like they have in numerous other countries. Uhuru Kenyatta borrowed a **** ton of money from the Chinese, much of which he kept for himself and his cronies, in order to hire Chinese companies to build stuff using some local Africans here and there as the help, and now the new government is struggling to repay the loans. So what are the Chinese going to do? Take the collateral - namely the ports. This is a very common Chinese strategy.
The US has experience with this already. For example, Illinois sold off a portion of a highway that connects Illinois to Indiana. The toll about a decade or so ago was 99 cents. Then it was sold/leased to a German company for something like 90-100 years. They immediately increased the rate up to $2.50. Now its over $5 for a passenger vehicle. A semi will pay over $40 - and that's just one way.
become a diversified economy with very limited success so far
That's because all they know is how to trade goods and run a store when they're not busy snackbaring 5x a day. They wouldn't have a clue on how to build an airplane or an MRI machine, or build an automotive factory. They hire primarily westerners for anything that's high tech, and people from phillipines, Pakistan, india, etc for construction, home health care and other jobs. They're basically giant gas stations pretending to be sophisticated countries.