If speculation was mostly responsible for the rise in oil prices, then massive intervention by a central bank shorting oil should be enough to drive prices down. But this hasn’t happened. So, either they don’t want to intervene (doubtful) or they know that intervening would do little to lower prices.
The Fed and other governmental entities certainly seem to have intervened in the stock market at times to stabilize a teetering market, something half-jokingly referred to as the actions of the Plunge Protection Team.
But this hasn’t happened with oil. Which leads credence to the view that decreased supply and increased demand, not speculation, are what’s pushing prices higher.