Probably due to low marketcap of whole crypto industry, it's easy to manipulate such low volume market when you have money (there is also media manipulation).
There are so many variables that could be fit into a regression equation and you would come to know that they are still not enough to explain the volatility impact of the cryptocurrency. So it is quite obvious that holders who have large volumes of coins could be one among so many other factors. The fact that the markets of Bitcoin are liquid is another reason and the list continues.