Because the crypto market is primarily bitcoin, it dominates.
Therefore, the global trend of growth or decline has always depended and will depend on the price of bitcoin, because it contains the main finances.
Thus, we always see the dependence of other currencies on the bitcoin price.
The price of Bitcoin can be attributed to so many thories of determining what is responsible for the movement of Bitcoin influencing altcoins to move in the same or similar patterns. The fluctuation in the price of Bitcoin can be base on the Buyers and sellers theory which constitutes the inbalance forces that move the market into opposite directions.
The strongest force between the both will push the market to it part as long as the force keep on dominating making it hard to analyze the market if the trader is not equipped with necessary information that could show or guess the direction of the market.
Bitcoin being the father of all cryptocurrency following the patterns and Blockchain interface make it easy for other coins to exhibit the same features that Bitcoin undergoes.