Since they have been paying a 3rd party production company to handle the publishing and social media which included the YouTube svc backed into the cost, my theory is they either stiffed them on payment or the production company had its own financial issues and got the lights turned off themselves.
This sounds like half the story is missing. YouTube won't just close the account unless it broke some sort of rule. So what rule was broken? Or it's what was written above, these guys didn't pay their own production company so the production company deleted all their videos themselves.