Because they owned every step of the process to make steel like for example they owned the mines to mine the iron. Then they would own a 2nd mine to mine the coal for the steel. Then they would own the factories to make the steal. That is a vertical monopoly so for shorting your answer you can say they owned the mines and the factories to make the steel.
The allies instead of providing a peace settlement based on the 14 point plan as Germany had though instead made the treaty very humiliating with the aim of keeping the Germans down. (C)