Last year the causes of bitcoins price going up and down were due to positive and negative news, the market was very sentimental, if there was good news the market would grow huge and if there was bad news the market would fall a few percentages, now it is unfortunately very different, the market barely reacts on positive news but reacts strong on negative news, whales(big investors) have a hand in this, they control the market based on the news, hence there is a good reason why the market is going up and down.