The value of an altcoin is strongly linked to btc value but not only. If it has a strong "background" (community, devs, marketing, wether it bring something new technologically and to the people..) like Steemit. Then it can grow almost independantly of bitcoin value.
That's how it should be, but it seems some investors do not check too deep. I hope the value of Steem will eventually reflect the quality of the tech