Zero's power rankings are based on the only stat that other than wins that matters in football, the clearest indication of a team's likely ability to beat another team, the passer rating differential. Look at end of year last year, all 4 teams that played in the championship games were top 10 in PRD, while 3 (GB, SEA, NE) were top 5. If you look back over the years, the same trends hold true.
PRD gets better as the season progresses/the sample size gets larger.
As any economist with a brain will tell you, past performance does not guarantee future results, so ranking Seattle high at this point of the season based on how they did the last few years doesn't make much sense. Especially when you look at historic trends for teams that lose the Superbowl.