Rize managed more than $450 million across its 11 ETFs through the end of August.
Some money managers were well positioned to take advantage of a court victory by Grayscale Investments.
Cryptocurrency advocates have been eagerly waiting for the regulator to approve the first spot bitcoin ETF.
The Long Cramer Tracker ETF has gained about 2.2% since its inception five months ago.
Grantham is one of Wall Street's most well-known bears, famed for his gloomy forecasts.
Some of the biggest ETF companies are relying on the success of one key fund.
More than $1.8 billion came out of the $39 billion iShares 20+ Year Treasury Bond ETF last week.
PGIM Fixed Income is among fund managers looking to capture windfall profits with 20-year bonds.
U.S. regulators have yet to approve a spot-Bitcoin ETF.
Naysayers are skeptical that a U.S. spot bitcoin fund would be a true game changer.