1. Be early - Fred was one of the first VC bloggers to give people a real time glimpse of his thoughts.
2. Be consistent - There were some notable VC's who blogged before him, but none with the daily pace he has consistently met for years. This regularity is hugely important.
3. Be successful - He has amazing credibility based on his investment portfolio. With their thesis driven approach, USV has assembled the best collection of "Large communities of engaged users" in tech. He has also invested in companies that have become some of the biggest brand names in tech e.g. Twitter/Zynga.
4. Be talented - I can think of a few VCs that meet most of the above criteria, but Fred is a really good writer with a strong POV. He almost always brings a fresh thought to stale issues and rarely uses his blog as a commercial for his investments.
5. Be Human - If you read Fred's blog you know what music he's into, where he vacations to, what his kids are interested in. He's a full personality, not just a repository of info about term sheets or financing structures.
I think the points that the OP makes are important, but are not the primary cause of Fred's success.