The defense has only been great against one bad and injured team
Watching the Seahawks in Week 4 it might be to get disillusioned by just how great the defense looked. While Seattle's defense has improved in each game as far as yards allowed, they still gave up 378 yards to the Panthers and Carolina is 25th in total yards through four games. The Panthers have also not gotten more than 281 yards in any other game. Carolina scored 27 points against Seattle (admittedly, 7 of those points were in garbage times) and they haven't scored more than 17 in any other game.
The Giants offense is just atrocious so not stopping them would have been embarrassing. New York is 31st in yards and last in points scored. Still, the Seahawks did their job and sacked Giants quarterback Daniel Jones 11 times and Seattle stuffed the run. The performance was fantastic.
But is Seattle really that good or did they just go up against a horrific offense? A good indicator might be how well the team plays in Week 6 against the Cincinnati Bengals. The Bengals are surprisingly struggling but still have high-end talent. They are somehow 31st in points scored but they could put up a high number if the Seahawks defense slides from its Week 4 level.
Seattle only plays three current top-10 offenses the rest of the season and they come in consecutive weeks from Week 12 through Week 15. That four-game stretch against the San Francisco 49ers (twice), the Philadelphia Eagles, and the Dallas Cowboys could make or break Seattle's season. And Seattle's defense has to be playing very well during those games for the Seahawks to have a chance.