The main factors that makes the price of bitcoin to fall is the FUD created by those big players like whales that taking the opportunity on the weakness of small time investors. Once the weak investors will get in panic selling this can easily fall due to lack of demand and the price will contentiously lower until such time whales will buy at cheaper price. I think this can be prevented if the demand will increase as more people will buy bitcoin and the supply of bitcoin will scattered around the world.
In fact so many reasons are there which causes the price to fell down, whales always effect the bitcoin price but I think that the most important fact is that of the bad news that people spread in the market in fact they want the price to fell down so that they may find an opportunity to buy bitcoin in a low price.