Obviously, it's no hidden truth in this market, even a newbie in the market knows this. When bitcoin is bullish, you would see all the coins soaring to new highs each day while if the market falls and bitcoin becomes bearish you would see every coin seeing new lows each day and falling even harder than bitcoin itself. This is why I suggest every mid term trader should always keep at least 50-70% of their portfolio in bitcoin only to make sure you don't fall for the trap of the bear market, when the market would fall your portfolio would look too red if you are not having a heavy proportion in bitcoin and whenever market will start to rise it will always start with bitcoin rising first.