I am wondering why Bitcoin price is much more volatile than the stock market?

Let's just stick with Bitcoin only.  Bitcoin have a market cap close to $1T as we speak and, yet, its price is still so volatile.  Is it because the availability of bitcoins in the market is low as most people (especially the new institutional investors) are hodling? 

Is it fair to compare Bitcoin (or crypto market as a whole) to a stock market like SP 500 (which currently has $31.61 trillion market cap)?  If so, Bitcoin cap is only 3% of the SP500.  Is it because of its relatively lower market cap which make it easier for its price to be manipulated (i.e., by a pump-and-dump)?

What do you think?