Bitcoin is only indirectly related to the stock market as a substitute store of value similar to gold and silver. When the stock market crashes, some usually switch their stocks into more stable stores of value. Bitcoin can be a great growth value commodity but the volatility right now relative to gold prices makes it less of a store-of-value, but when adoption increases price volatility should decrease.

Short term price fluctuations can be from high volume traders picking up Bitcoin during dips and times of investor fear, however in the long term the price has always been rising. In the long term the deflationary protocol releasing fewer Bitcoins per block verification will lead to nearly zero or negative inflation.