Piracy

Shutting down the entire subreddit would have been worse

How? If shut down, then there would be no forum. And the other option, there was the appearance of a forum, where nothing of substance about the topic it was founded upon could be discussed.

This wasn't about people posting torrent links (or not just that). They were nuking all sorts of shit. Discussions of when torrents might become available in the future, technical details on how anything worked, release names. You name it, anything of interest was gone (and that's only from that point going forward, literally everything going backwards was scrubbed and scrubbed hard).

When a large social media platform continues to exist, even if it's bad, even if it's unusable... it sucks the oxygen out of the room. Often making it impossible for anything else to take its place, even if that substitute would fix those problems. By keeping that forum around, it starved out other possible venues for years.

It wasn't the right call. It just happened to be the only call where he got to continue to "be in charge". Which is the thing he's most concerned about here, with this post.

and the old posts were archived, so the post link removal is not an issue.

That's great for historiants in the 26th century, they have access to all of those posts. For the vast majority of human beings alive today, they are effectively gone. They cannot be found without extraordinary, heroic efforts. Which no one will bother to do, because if they knew what it was they were looking for exactly, there'd be no reason to search in the first place.

"Don't worry that he burned down the public library, some millionaire book collector who lives in Europe somewhere has private copies of all the rare editions!"

The talk of an exodus being possible in the first place here, is because it was not shut down back then.

That exodus happened way back then. Just no one noticed because they had a heavily-censored forum with enough activity that it looked like something was going on.