Smaller cryptocurrency with a lower market cap can be manipulated by people that have thousands of Dollars to invest , but a coin like BTC can not be manipulated by anyone because of the huge market cap.
Big investors and influencers can manipulate the market anytime they want. When you have $100 million to invest and you invest in a certain coin, the value will jump, once it reaches high, you can sell your assets and move on, all the while the price for that coin will go terribly low.