Panic selling is what draws the price of Bitcoin so down to the drain. Any event which leads to panic selling of Bitcoin can be considered as a contributing factor. The news of a hacked exchange site, false news from governments, banks and the media, a Bitcoin advocate country later banning Bitcoins etc. All these factors contribute to the fall in price of Bitcoin on the market.
We cannot blame everything to panic sellers, it is true they make the price to go down but that is not all, the price is also affected by the lack of demand and when people began seeing the price of bitcoin going down they decided to wait and stop investing, this simple detail pushed the price even lower since no new money was being invested in the market.