On a daily bases, there are millions of people who are buying Bitcoin regularly, so, there is always a steady in-flows and out-flow of money which contributes to the daily market swing of Bitcoin. If there is a huge push up in price or a downturn of the market, that is when people will actually begin to look for the factor that contributed to such dump or pump but for the normal little price volatility, it's normal for Bitcoin's volatile nature and it's caused by demand. Other factors that contributes to high volatility is either a good economic news, huge dump by whales or when huge sum in also bought, etc.