Unfortunately, there has been a few YouTube channels hacked within the last few months. The most recent of which was Linus Tech Tips. LTT has over 15 Million subscribers on the platform and was recently hacked via a PDF file containing malware that stole an active session token from a web browser.
Whilst this sounds scary, the attack would have been stopped by step 4, not messing with suspicious emails, but mistakes were made and the channel was hacked to promote a crypto scam. Thankfully, 24 hours later, everything returned to normal, but not before a large portion of the channel's videos was deleted.
Linus has called upon Google to change the way that Google deals with security breaches, and offer more features to help further boost account security.