Since all coins are traded relative to bitcoin, the price of other altcoins changes with the fluctuation of the bitcoin exchange rate.
This is my essence of my question, why does other coins follow BTC exchange rate given that other coins (not tokens) follow other protocols than BTC?
If i understood your question right, you practically asking why everything falls down when BTC does? If so, I can say, that BTC is representing all cryptocurrency market. The reason is, something about 40-50% of operations still involve Bitcoin. It`s like reserve currency of the market and so everyone reacts to it`s price falling like if market itself is falling.