Most of altcoins' prices are generally affected by a change in bitcoin's price. That's a fact since all are paired with bitcoin in exchanges. While for some that continued to rise during a fall in bitcoin, they simply have showed improvements/developments in their projects such that many investors are attracted. But this doesnt mean bitcoin will be outruled by altcoins. Just wait for a massive pump in bitcoin and you will see its dominance.
Bitcion price is the over all controller of cryptocurrencies and so Altcoins follows but they have different methods of promotion in such a ways Altcoin also brings to the market with more population and becomes a fast running in crypto world.