Bitcoin moves altcoins will move as well either to go up or going down so that can be a good correlation between these two. Any market can’t stay on the top for a long time because they have to go down as well, there’s no fixed price in the market everything has to move and the volatility of the market is getting higher every year.
And what better example we can ask of that correlation than what it is happening on the market right now, take a look at the top 100 coins and their 24 hour growth which has been impulsed by bitcoin, this is the first time we have surpassed the 14k level in a long time and there is now a significant possibility that if the price can remain there we are going to make an attempt at the 20k level, what it is going to happen once we get there? Personally I think a decrease in the price is in order since most people will be afraid of the price crash and they will push the price down but with bitcoin you never know, since we can actually reach a new ATH before the end of the year.