Are these Youtubers not using cellphone verification to log in in their gmail serviced site like Youtube, I consider this negligence if you are popular you know that you will be targeted and this is one big reason why you should secured your account, hackers are very good right now if they can still hacked account that are cellphone verification secured.
Those affected YouTubers probably have (or atleast should have) 2FA protection enabled, but what those hackers usually do is: they contact YouTubers asking them to advertise their software. They install that software to check it out, but what they do not know is that it is malware infected, making them loose access to their account and channel. Many of them are simply not careful enough and not aware of all the dangers of installing unverified software, and that's why we have so many of them hacked lately.
