Do they really? I often encounter this statement. And i have no idea as to why. This past few days, bitcoin is on the rise and most certainly than not altcoin's price surely follows. I am not saying this is bad but altcoins have very little in common with bitcoin. And they are certainly not carbon copies of bitcoin either. Why the heck is their price so closely connected despite being so fundamentally different?
because the market is very bound by bitcoin. this is the fact.
you can see if bitcoin goes down, it will have a bad impact on the altcoin, and so does bitcoin rise. altcoin can get worse. so when bitcoin tends to be stable, that's when the altcoin will be pumped.
I think you should try to learn how to analyze