Perhaps he realises that other people are doing it too and, as you said, realised the more people who do arbitrage the more it goes away. He could be out to sta

Perhaps he realises that other people are doing it too and, as you said, realised the more people who do arbitrage the more it goes away. He could be out to stabilise the bitcoin exchanges as well as provide liquidity to the market. Perhaps as more people use it, the demand for bitcoins go up also, and since limited supply the price goes up. And he might have substantial holdings of bitcoin he wants to sell. More people trying to find arbitrage opportunities makes it easier to sell his bitcoin which are now higher value.