As a king it controls the younger ones who were just given birth. The altcoins are just need to the system and they have not known the left and right of the ecosystem so they have to follow the step of their father Bitcoin and their mother Ethereum. And direction Bitcoin follow they also follow, when the price of Bitcoin rise they follow and the price reduce they reduced too. Bitcoin has a great positive effect in the cryptocurrency market.
Those who are investing in altcoins also monitor the price of Bitcoin to see their coin improvement. Last week Ethereum price was $2340 and Bitcoin was $44+k now that Bitcoin has come down, the price of Ethereum is $2100 it has come down again and other coins are also down.
Bitcoin is a cryptocurrency that heavily influences the market - but doesn't control anything. Traders and investors consider bitcoin to be the best benchmark in the market so its price volatility can impact altcoin prices. Bitcoin's market capitalization is much larger than others - so this is also the reason why bitcoin is a benchmark for altcoin price volatility.
I don't agree when you say bitcoin controls the market - that's never true. Crypto trading is done freely and is not controlled - but manipulation is possible. The average altcoin trader and investor uses bitcoin as a benchmark for analysis when they want to invest in altcoins - but that doesn't mean bitcoin controls the market.