In my own opinion I believe bitcoin controls the market, whenever bitcoin pumps most of other altcoins also pump and whenever bitcoin dump most of other altcoins also dump. Bitcoin is the master of cryptocurrency and it controls the market that's why it will be rear to see a coin pumping whenever bitcoin is dumping hard. I don't say there are not some coins that will still pump but they are very rear.
Because until now Bitcoin is still in the top position and Bitcoin dominates the market, therefore the price of altcoins is usually affected
by the movement of Bitcoin. So when we are going to decide to invest in altcoins it is very important to see the movement of Bitcoin as well,
as you said it is very rare that altcoins can pump when the Bitcoin price dumps. It is very natural that Bitcoin is very influential on
the crypto market, because in addition to Bitcoin being the first crypto coin, Bitcoin does have the most supporters in the crypto world.
So if there are people who don't invest in Bitcoin, it's very unfortunate, because besides Bitcoin is the best asset so far, Bitcoin is also
the safest to buy. Because no matter how deep the Bitcoin dump is, it will always be able to go up again and even reach a higher price.