If I remember right, Digg was a combination of changing the UI drastically in a way that most everyone hated, combined with "power users" having disproportionate ability in getting posts visible.
It's not just that, the new UI hooked the marketers directly in as feeds. So a blog or publication would be something you'd "follow" and upvotes/downvotes as you like. This scared the power users who were no longer the submitters, and also balkanized the experience and gave ghe users the impression they sold out to the actual content creators instead of the users.
Simultaneous with this, they even disabled the comment history. Like you couldn't see what you had commented or what peoples' replies were, unless you were in the thread.
Took several months to get that back, and by then it was too late - all the real content creators had moved to Reddit.
> If I remember right, Digg was a combination of changing the UI drastically in a way that most everyone hated
Although this is common belief, Digg was on the decline well before v4 was released. v4 was a response to the decline, not the cause of it.
They mistakenly attributed the site's decline to the rise of social media apps like Twitter, and v4's was their attempt to become the "Twitter for news".
It's true that Digg didn't do enough to foster a healthy community; threads were often toxic, and yes the top users had too much sway. What's forgotten is some of the dumb things they did to try and monetize, like that full-site ads (background image ads) that I'm pretty sure everyone hates.
Even though Digg was on decline, it was still bigger than reddit. It could've still been a significant site today, or at least something like Slashdot. The day v4 was released, it singlehandedly killed Digg. It was a bloodbath never seen before, or since.
> Even though Digg was on decline, it was still bigger than reddit
It most definitely was not. reddit was already bigger than Digg long before v4 was launched. v4 did cause a bump in reddit's traffic, but it wasn't nearly as significant as people think. Most Digg users were already reddit users too. In fact, a lot of the power users were getting their stories from reddit.
That's why at the time the joke was that if you wanted to see a summary of reddit the day before, you just looked at Digg.