Mostly because bitcoin (BTC) still acts as sort of the "index" of the cryptocurrency space (just like the SPY with stocks), and that BTC trading pairs have the most trading volume and market liquidity. Like it or not this is not going to change any time soon.
Because of exchange bot trader. The bot determines if the sentiment of the market and reduce the order that they set in accordance to the sentiment. That’s why most of coins move on the same direction except for those token that has an active trading activities against the trend like when the project has big announcements or exchange listing which gives the sentiment signal to the bot.
Market makers on exchange is made bot and only few of them is from traders.
Sorry but, wtf is this??