Their automated system makes mistakes more often than people think. A youtube account can get suspended or even banned for no reason that seems obvious to the user. But here's how to avoid it in the future
https://gologin.com/blog/youtube-account-suspended-or-banned/ . When you manage multiple channels from the same browser or computer, YouTube treats them as connected. One account violates a policy and the rest get swept away too. No warning arrives beforehand. Everything just disappears overnight.