Reddit Migration

Here's another contemporaneous article with a good amount of info: https://searchengineland.com/digg-v4-how-to-successfully-kill-a-community-50450

Personally I like this summary from a Harvard student assignment:

In August 2010, Digg attempted to wrest control back from its power users by migrating to a new system (Digg v4) that deemphasized user-contributed content in favor of publisher-contributed content. The change incited an uproar among power users and regular visitors alike, who felt the company was selling out to the mainstream media it had originally sought to replace. Digg experienced a mass exodus of users, many of whom turned to rival site Reddit. While Digg’s traffic fell by a quarter in the following month, Reddit’s traffic grew by 230% in 2010. Digg never recovered from its transition to Digg v4, and the site continued to bleed users and traffic over the next two years. By July 2012, the time of its sale to Betaworks, Digg’s monthly unique visitor count had fallen 90% from its peak.

Know Your Meme also has a surprisingly good write-up.