The attitude of the government and the law to Bitcoin has a great influence on this.
Hacking (hacking), although this is not a definitive factor, once Bitcoin is stolen, especially at a certain exchange, many Bitcoin players lose confidence in Bitcoin and form a sell-off.
There's a big factor that affect to the bitcoin price if people are lack of knowledge through cryptocurrency and they really don't believe that the bitcoin will never be crash. Panic selling is one of the factors that affect to the bitcoin price. They do panic selling because they are afraid that the bitcoin will going to crash. The negative news and FUD that poisoned the mind of the people to do panic selling and dumping the bitcoin price.
Yes lack of knowledge makes people think negative which decrease the people who are investing in bitcoin because they think it is just a scam or maybe some of them thinks that bitcoin will keep on falling so they sell at panic, and panic selling is the main cause of falling price of bitcoin, high supply and low demand also effects the price of bitcoin.
Agreed, the factors that affect the value of bitcoin is the media and the people behind those speculations, the negative comments of people that make the investors and holders do the panic selling, so the market go down, some of them have done stupidity, It cause the breakdown of market, almost all alts and bitcoin has dip its price.