This video explains the situation nicely. I'll leave a TLDR below as well.
TLDR the account is hacked, the creator, Astartes40k, has all his work taken away and youtube is doing nothing about it.
Don't trust anything that comes from the youtube channel, check his twitter or Patreon for updates. Please don't give the hacker any ad revenue and spread the word about this to others and youtube.
(other videos on the hacking from Arch Warhammer, Chapter Master Valrak and TheQuartering.)