Well, as much as I know that, the price of bitcoin is determined by supply and demand, I also had to see some reasons with that threads op as to the possibility of some people(whales) being able to manipulate these supply and demand and judging from how the price of bitcoin could easily be affected by a tweet from President Donald Trump, has given rise to some sort of curiosity in me to ask and know if truly that some group of people can actually determine the price of bitcoin by altering the demand and supply of the coin?
Yes but it mightn't always be people but sometimes exchanges are guilty of this. Exchange have numerous bots that helps keep the market active by creating buying or selling orders and sometimes this bots are being used to manipulate the price of Bitcoin. For Bitcoin though, the manipulation doesn't last because while you're busy creating selling pressure, there are other people creating buying pressure and this is countering any plans you have for the market. All types of markets can be influenced at a particular time but it depends on how mature the market is and the volume the market has for we to determine how impactful the manipulation is going to be. All market can be manipulated and Bitcoin is no exception.