digg followed StumbleUpon (https://en.wikipedia.org/wiki/StumbleUpon https://en.wikipedia.org/wiki/StumbleUpon). StumbleUpon was the source of the vast majority

digg followed StumbleUpon (https://en.wikipedia.org/wiki/StumbleUpon https://en.wikipedia.org/wiki/StumbleUpon). StumbleUpon was the source of the vast majority of digg and reddit content before people like Randall Monroe were making high quality comments on reddit. Once every reddit post had a literal expert respond with high quality comments, it dominated the others and content began to be posted on reddit first, rather than the content being found on stumbleupon or digg and ending up on reddit. Eventually things like askreddit became popular and community style content flourished.