because bitcoin is not a stable price ,its depend on how people to buy and to sell bitcoin its form investors ,sometimes they will panic selling cause of changing his price ,there is no asurance about the price of bitcoin
panic selling usually occurs when whales doing big sales to capture profits and then buying back at a lower price..
As Bitcoin is a decentralized coin and no one can control it completely, that's why Bitcoin is so unstable. But price depends on the user that supply and demand ratio.
this is the most appropriate reason, Bitcoin is a decentralized coin where the price change is influenced by the amount of market demand, we will not be able to hold the Bitcoin price stay at the price of $ 10k when the market demand increases or decreases..