hello friend,
in 2017 I was very happy when I saw the price of Bitcoin increase in coinmarketcap because when the price of Bitcoin increases, then the price of Altcoin will immediately increase too, but for now when the price of Bitcoin increases and it does not affect for the prices of Altcoin (even still down), then when the price of Bitcoin goes down and at that time the price of Altcoin will go down too, so I do not understand the current state of the market and what is happening right now.
You need lot of information to understand that the market iis always fluctuates. If you ask why the market is always down then go up it because market is depending to what's in demand in the market. Bitcoin and altcoin will not same but as you see that bitcoin is increase and the altcoin in not because many investors buy btc and some are in altcoin. If bull run comes you will see the changes bitcoin will up and altcoins will follow.