People follow him because he is the biggest man in cryptocurrency What he says happens. Is one of the people and when he speaks it is clear and easy.
He is a successful man in cryptocurrency The coin he talks about gets his price up. a few days ago he tweeted about dogecoin and check his price where are you. I think that's why people follow Elon Musk.
My own opinion is that some people take advantage of this momentum to get a profit where they invest in coins bought by Elon Musk. those who followed thought that there would be a famous person and bought a lot of coins.