Couple of things here: they only pushed the price up by a buck. They essentially made money by first buying futures that predicted the price would go up... then bought 2/3rds of the production out of Cushing. That created the impression of a shortage, causing the price to go up. They then sold their futures, making a bunch of money. They then bought shorts, then sold their positions at Cushing, creating a glut and making a bunch more money off the shorts.
But they made their money on the size of the shorts and futures they bought, not on any real increase in the price of crude. It was in volume.
I'd also say the investigation is politically motivated. Obama has been going on about how it's all the speculators' fault, and now the CFTC has found some speculators to pin the blame on.
But like I said above, they bought a massive position, but only pushed the price by a buck. The market tries to find the ideal price. The speculators are a key part of that equation.