Investors have piled into a recently launched bitcoin exchange-traded fund (ETF) that’s designed to profit from price declines in the cryptocurrency – to the extent that the vehicle is now the second-largest bitcoin-focused ETF in the U.S. market after just a few trading days.The ProShares Short Bitcoin Strategy (BITI) ETF raked in the equivalent of 544.2 BTC, or $11 million at current prices, making it the second-largest exchange-traded bitcoin fund listed in Vetle Lunde, an analyst at Arcane Research, noted.