the cause of bitcoin volatility, as it is affected by the news that scares the bitcoin users that bitcoin is likely to be governed by the government, the security vulnerability makes investors react, making the bitcoin unstable. Tax imposition on bitcoin also affects the volatility of its price.
I agree that bitcoin volatility is caused by people who sell during the fall and many investors take opportunity for the time like that as it will surely give them profit. Government also cause for that volatility as they want to control on it. Also there is correction to it for more security. The more that users increase the more that many strive to have it.