The photobombers may have hoped their guerrilla stunt, which lasted only about a second, would counteract some recent bearishness in virtual currencies that has driven a month-long selloff. Cryptocurrencies as a group have lost 23% in value so far this month. Bitcoin is down more than 20% since its peak of $3,000 in early June, while Ethereum's price has fallen 50% since its high of more than $400 around the same time.

http://fortune.com/2017/07/12/bitcoin-buy-yellen-fed-testimony/