1. Because the price of bitcoin and equities have been strongly correlated in recent months. Because the stimulus package would be a boost for stock markets, it should also be good for the price of cryptocurrencies.
2. Crypto investors have been betting all year that the flood of government and central bank spending to fight the pandemic-caused economic slowdown will eventually lead to inflation, which would also be beneficial for cryptocurrencies.
3. All the stimulus is calling into question the independence of the U.S. Federal Reserve, which in the interest of preventing economic ruin in the short term has been basically printing money with abandon, leaving itself open to criticism about the mountain of debt these spending sprees is creating.
