I really have to challenge point 2. The way you write it completely downplays the hard work digg & co put into their product. It was innovative and successfully branded. Not so simple IMHO. Neither do I think digg was intentionally marketed to 15 year old gamers. Of course, correct me if I'm wrong; I well may be. If kevinrose here is kevinrose, he'd have a better story to tell.
Specific groups can be attracted to a site by a graphical look of a site alone. I think Digg vs. Reddit is exactly about that.
The only thing that I still don't get is excess of politics on Reddit. Maybe it's just those who are interested in politics have one thing in common with most geeks: the lack of artistic taste :)
