One of the first post-mortems and note the date on the article.

Within a month Digg went from the mover and shaker of the Web 2.0 Buzzword bingo to a pariah. By October, traffic was down 80%. By the end of the year the place was abandoned. It feels like this was a million years ago, but it was only half a decade ago. The implosion was so fast, and so total, it made the "real world" news.

The redesign killed the community

Fark went through a redesign and a change of layout a few years later, and they made sure to keep their users engaged, and went through the whole process slowly and had no serious issues coming out the other side. Digg.com is stil la thing, but barely in the top 100.000 websites in the US.