Here is why they are so good:
1. They really underachieved last year. Prior to the start of the season last year, most people picked them to easily win the NFC West, and win somewhere around 10-12 games.
2. They actually have a good coach now
3. They have a coach who can call plays that fit Alex Smith's style and the 49ers offense.
4. They have had a pretty soft schedule. They've played the Seahawks, Bengals, TB Bucs, the Browns, and the Eagles when they were really struggling. Still don't know how they lost to the Cowboys when Kitna played part of that game because of Romo's rib injury.