The major factors affecting bitcoin are :
Change in government - it's simply means when another government enter there's will be reduction or addition of some policies.
Political instability - when political system in the country is not stable, everything will get down.
You should not forget about the minor factors that can affect bitcoin, such as the news on the internet, because we already read about that a long time ago. And in a few months ago, we also read about the news and some of that news make the bitcoin price jump to the high price and suddenly, the price is down until the current price. But that does not stop bitcoin from increasing, especially when the adoption still continues because it can give bitcoin price to raise more.