Firstly, I think that there is very little tangible correlation between the traditional stock markets, and bitcoin. They are simply operating in two completely different fields here, stocks represent equity in a company, while bitcoin has the utility of facilitating transactions without intermediaries, as well as a coded in supply curve which can't be manipulated.
Correlation isn't about how similar two assets are. It's about
how similarly their prices move. Stocks are obviously a different type of asset, but what matters for correlation is that both stocks and Bitcoin represent
investments. People buy both types of asset to speculatively profit, draw returns, or to beat inflation. So while we shouldn't expect the stock market to
cause price changes in Bitcoin, we should expect both markets to
react to variables that could cause a flight to cash and away from risky investments. A financial crisis like 2008 could result in that kind of situation.