While Jamie Dimon, Warren Buffett, Ray Dalio and Larry Fink have all revealed themselves to be skeptics of bitcoin, accusing it of being a bubble, at best, and a fraud, at worst, one longtime investor who made his name scooping up “value” stocks in the 1990s has quietly posted astonishing returns betting on the digital currency, predating a wave of more than 100 asset-management shops that have sprung up to manage portfolios of cryptocurrencies.