There's a difference between making 1000%s on speculation vs 70% on arbitrage in terms of risk -- not to be rude but when he talks about naive investors I think this is what he's talking about.
He's not "on the short side". If you read the article, he's talking about an arbitrage opportunity, which if executed properly, should not be net long nor net short.
Citron is on the short side. Their entire investment strategy of the company is to short assets, in this scenario the future is used as an arbitrage hedge, but overall yes citron is short biased on bitcoin.
Citron is not bitcoin neutral. They are short biased bitcoin as their website and twitter account reiterate. And a hedge doesn't mean "neutral." It simply protects you in the event that an investment doesn't go as expected.
The bloomberg piece says: “Left recommends shorting the trust, buying bitcoin futures”. He says in the video: “I don’t even care what happens to bitcoin”. Where is the short bias?
A year ago, no one knew the price was going to go up 1000%, so some amount of luck is involved. Price could have just as easily stayed the same or even gone down 90%. If you bought in there is some amount of risk involved.
The 70% profit made by an arbitrage opportunity doesn't require you to guess where the price will go in the next 12 months. You know for a fact that as long as neither of these companies go bankrupt, you'll be making 70% on your investment.