William E. Seale, Ph.D., Chief Economist of ProShare Advisors since inception and ProFund Advisors LLC since 2005. Dr. Seale has more than 30 years of experience in the financial markets. His background includes a five-year presidential appointment as a commissioner of the U.S. Commodity Futures Trading Commission and an appointment as Chairman of the Department of Finance at The George Washington University. He earned his degrees at the University of Kentucky.

The introduction of futures didn't lead to a wave of hedge-fund money shorting bitcoin. It led to retail and institutional money going long bitcoin. We talked last week about the spread between Cboe's bitcoin futures price and the actual price of bitcoin, which was wider than $1,000 for a while. The spread has tightened considerably -- as of 8:15 a.m. today, the CME futures traded at $18,585, Cboe futures at $18,670, and spot bitcoin at about $18,245, for a spread of about 2 percent -- but it still exists. Why would you pay more for a synthetic bitcoin in a month than you would for an actual bitcoin today? The answer, presumably, is that the synthetic bitcoin is more valuable to you: You want bitcoin exposure, but you'd prefer to get it through a standardized contract on a regulated exchange that settles in dollars. 
The idea is simple; if the future is trading above the underlying asset (Bitcoin) today, we buy the asset and sell the future, thus receiving cash and locking in a profit. Then on the delivery date, we sell the bitcoin to cover the costs of settling the futures contract. For the deal to be profitable, the price difference has to be large enough to cover interest between today and the delivery date as well as all costs fees.
There's a lot of ins and outs which can get confusing in arbitrage trading. We won't go into the technicals of why futures contracts trade at a premium to spot price. You can read a full explanation here. If it's not of interest to you, all you need to know is that there's a tendency, the further out in time the futures contract expires, for the premium to spot to be higher and higher in nominal percentage terms.