Powerful person by their assets and money but i think its not excuse to play the market because of their posting on social media. But of course its up to traders if they bet what they have,and listen to this billioners people to what they posting on social media.
If you're talking about the recent tweets that affects crypto market then the problem isn't really those billionaires but he people who just take these billionaires tweets too seriously. I mean, People like Elon don't even tell people to pump dogecoin but other ordinary people still buying it out of their own intiative anyway. Maybe he's a bit manipulative but if people don't consider every of words coming out of his tweet as a trading signal then he won't be able to manipulate the market.