I think there are some reasons for this:
1. The market depends too much on bitcoin. That is the face of the market, when it comes to technical dollars just think of bitcoin. It has surpassed real value and is manipulated by some forces, with limited application but a currency to convert to other currencies. Therefore, when the information is not favorable with bitcoin, the market is affected.
2. Many investors lack basic knowledge and skills, they only invest in large numbers. When bad news emerged, they lost faith and immediately started selling off to stop losses causing a sharp decline in the market.
So when investing in money you should thoroughly study them about the applicability, technology, development plans, developers. I mean the money with new technology and widely applied as Ethereum or Arcblock will be very potential and stable development.