When people add you as a mod, you can still leave. He never did. That subreddit in particular was known to have the blessing of the reddit admins to operate and eventually made 'subreddit of the month'. Then a news org picked up that reddit was hosting this content and then they shut it down.

They were well aware of what was going on. Andrewsmith is right, there is some plausible deniability there, but with the everything else we know about Steve Huffman, I'm not so sure I can agree with his assessment that it was forced upon him.