There are so many reasons which are impact bitcoin for less value to more value like if the demand for bitcoin rise the price is moving to rise and till the market force like supply balance demand the price become less and unstable so it impact bitcoin. and with this the price volatility high and then the investors feel fear and they switch the coin. So in crypto bitcoin is the most important and valuable coin for now as we can say that in the future bitcoin will use for many purposes so it will make bitcoin more expensive.