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.
There are times as well when there is no significant news but then the price would suddenly go down. When the price goes up usually there is a news that is involved especially if it is a very significant movement but when the price goes down, there are times when you don't know any news that may be the reason of that change in price.
What you have mentioned are some of the major news that affect the downfall and if you are quick enough to catch the news then you would be able to be profitable just using this kind of news. Since there are different kind of trading then news base trading is still profitable especially in crypto market wherein news plays a big role.