Assuming your broker is competent (which the broker in this story is not), they won't let you buy 100,000 contracts for 1000 USD unless you can cover the potential downside, which would be of millions (possibly tens of millions) of dollars. So you can't actually leverage $1000 into going up for down $100,000; you would be tying up $X,000,000 to go up for down $100,000.

Unfortunately IB was not competent and they did not calculate the margin requirements correctly, which allowed their customers to leverage themselves improperly.