Because the cryptocurrencies are ruled by the Demand and Supply law , higher demand tends to increase in price and decreases when supply is not enough. The market of crypto is like a glass full of water that tends to overflow when added (mined) , now every movement in cryptocurrency can affects to its value.
In addition, we must not forget that the traders they are almost always trying to take advantage of market conditions to maximize their profits in the shortest possible time, also, The fact that the news circulates quickly through Internet they also sometimes cause prices to move very continuously going down then upwards depending on the veracity of the news is the result of those movements and its duration, another factor would also be that since it is a world market, some event somewhere stimulates growth or, on the contrary, a reduction in the prices.
There are 2 types about the news of Bitcoin and these types can affect the price of Bitcoin increases or decreases!
Rumors and real news, what is different between both?
Simple, rumor is also a news, but it does not guarantee the trust by anyone, but with real news, it has received high levels of trusted.
Fuds were all over even its at point of increasing theybsay it will crash, volatile is too hard to determine and it does affect especially newbies on how to react on it.