I've been monitoring the market for a couple of months now. Most of the coin value rely on the price of Bitcoin. If the BTC price goes up, every altcoins will follow and if it will goes down, the price of every altcoins will goes down as well. But the question is, Bitcoin price/value is still going up but the price/value of every altcoins especially Ethereum goes down. How did this happen? Any logical or scientific basis to explain this. As of now, I am still confuse. 
It's not magic, it's normal happened. Everytime the bitcoin price increase, other altcoins like ethereum, BCH and many alts will go up too. It's always like this since the market crash in the early 2018. I think it's because of bitcoin is the biggest cryptocurrency and bitcoin market is the biggest too.