I specifically remember one commenter saying, "Look, we're not happy about what happened either but we have no where else to go. Now scoot over."

Was the Digg exodus the start of Reddit’s Eternal September?

Traditionally Tumblr was blamed for that in the late 2010s, although Digg is plausible. I think the sheer volume of Tumblr had more impact on Reddit than Digg ever could have, its a size thing.

A lot of Reddit problems were own-goals. Lets have a civil war over being a free speech or being a brutally censored speech site, I'm sure the civilians trapped in the middle will love the experience. Spoiler -> They did NOT.

But humans can always be replaced by bots if you're selling advertising views, LOL. HN doesn't sell ads (or at least none have ever gotten past my ad blocker) so there's fewer bots here so the decline due to bots is slower here.