Isn't it obvious? It's all about money, of course. No one will ever miss an opportunity to earn money! When they upload a video, they get money for that. They are trading and making money in one way and also making money from YouTube another way. Yes, they are not all traders. Some big channel may upload a video promoting some crypto projects. But they are doing it because they were paid by that project. If you know their background and know that they are not traders and only promoting it for the money, then try to stay away from them. It will create a hype for sure, but as we all know, hype tends to die soon.

Personally, I never follow anyone related to crypto. You may follow some well known persons, but that kind of stuff is for short term gains. If you are a day trader, this may help you a lot. Because short term market movements are based on sentiments and trends. I always focus on long term gains. So all I do is buy and hodl BTC.

IMO, influencers are the cause of FUD and FOMO. So it is better to stay away from them and focus on long term investment.