Its not all the times price action of altcoins depend on Bitcoin. Actually depend on the trend of market, sometimes price of all altcoin triggered by Bitcoin, but in another times, both was move opposite. I have seen when BTC dominance reached 70% , BTC was bullish but altcoin dumped. But that happened in many times is alltcoin depends on BTC, price action of all crypto almost the same, like many whales trade using trading bots.