Yes, their Tweets will have a short-term influence on the markets.... but it might have a long-term influence on it being the currency for the future. (They also mix with very influential people in the financial world)
Everyone who really invest in crypto with good attitude will not try to influence other or tweet something which contain any suggestion with high risk. He really manipulate market to do what he did, and the reason why he did because it will add his own profit and never care what people get.