Investors are more certain that oil prices will increase—but the market isn’t playing along. : Hedge fund bets on rising Brent oil prices jumped to the highest in two months early last week, according to data released Friday. The optimism proved mistimed, with crude tumbling the following days as fears of emerging-market crises and trade wars led to a widespread rout of currencies, equities, bonds and commodities. The disconnect was the latest muddled sign for the oil markets.