Bitcoin price and S&P500 index are not correlated, I read so many of similar posts last few months but they are not correlated, just because both crashed in March and recovered since does not mean there is a correlation whatsoever.
It does. Correlation is about dependency. When one goes up, does the other go up and vice versa? The correlation between stocks and BTC is not perfect but it's very obvious.
Why would they suddenly become correlated when it wasn't the case in 2019, 2018 and of course 2017 
They've always been positively correlated, all the way back to when BTC price discovery began in 2010. I've discussed this at length in my thread. https://bitcointalk.org/index.php?topic=5196072.msg55178480#msg55178480