There’s a lot of incidents like this before, Youtube seems to be week when it comes to security, I guess they have to address this issues to avoid further scam promotions like this.
The only way to stop that is to contact Youtube, that’s a huge account and can easily attract newbies, I hope no one suffer from such scam promotions. For sure, regulatory agency will address that issue and will run after Youtube and askt their security protocols, that can be a big trouble for them.
All I know is the Youtube channel is attached to an email if the email security is weak there's a possibility of hacking, Gmail is equipt with text, 2FA, and other security measures and they will ask for security verification if you log in in a different IP, how com, these hackers able to bypass these security measures, they are really good at hacking so no channels are safe now if they can hack government channel they can hack popular channels too.