Scarcity gives a thing its value. This is the major reason that gold and diamond are expensive. Bitcoin as the pioneer cryptocurrency is highly limited in supply and I believe this has impacted its price. Therefore, we can confidently say the people impact the market and the market forces decide the price. It's a sentiment thing and nothing more to it. The same Bitcoin that was worth over $19,000 is now around $6000. Nothing has really changed except the people's sentiment towards it.