Billionaire Ken Fisher just turned Nvidia Corp's (NASDAQ:NVDA) latest rally into a $2.36 billion paper windfall. The fund manager is reaping big rewards from his Nvidia bet, as the chip giant's stock surged 18% from $157.99 on June 30 to $186.58 on September 30.Track NVDA stock here.A Massive Stake, A Massive GainFisher Asset Management owns 82.51 million shares of Nvidia, making it one of the firm's most prominent single-stock positions. As of June 30, those shares were worth $13.04 billion. Fast-forward t ...