So basically whenever bitcoin goes up, altcoin goes down and vice versa?
Yes technically if bitcoin goes up. Then we can say that many altcoins would goes dump becuase of many trades selling their altcoin and will affect theprice of it. And they will buy bitcoin as soon as it's lower and sell it high. So after bitcoin pump they will their bitcoins in higher and buying many altcoins that have affect in bitcoin pump
You noticed that during the last sharp rise in bitcoin prices, the situation was different. Alternative coins grew with bitcoin. I was alarmed by this fact