1_"Why is the algorithm of BTC built in such a way that it drives all other cryptos as it moves up or down?
Like "Would it not have been much better if BTC price movement do not effect every other cryptos?, So as when the price of BTC falls, other cryptos price will not but would be base on the amount of demand and supply present in them, just like the traditional forex market where all fiat currencies do not fall at same time.
You are misunderstanding bitcoin completely, bitcoin is not somehow manipulating the other coins with its code, if you think about it it would be very dumb for the developers of thousands of altcoins to somehow leave some code allowing bitcoin to manipulate their coins.
So what is actually happening? Bitcoin is simply too big, as an example think of bitcoin as the sun and altcoins as the planets in the solar system, even if the sun moves around the galaxy it has so much influence over the planets in the solar system that they move with it, bitcoin is the same, bitcoin has such a huge advantage over any other coin that if it moves then most coins respond to it even if their developers do not want this to keep happening.