After Bruce Irvin left the game with 4:01 left, Seattle completely stopped getting any pass rush. New England called 15 straight, non-goalline, passing plays as they easily marched down the field, twice.
Irvin is a good pass rusher but is he really that influential?

As a vet, he brings a lot to the team, but not really elite pass-rushing moves. Through 2 games, he had 5 tackles and 0 sacks despite playing <80% of snaps.
So if the Seahawks weren't missing his rushing ability, what changed with him off the field?

IMO, what changed was how often we called Tite, or at least Tighter, fronts. Through 3 quarters, Seattle lined up >2 DLinemen as 4-techs or tighter on about 1/2 of all snaps, to great effect: NE averaged ~0.5 EPA/snap less whenever they did.

With Irvin gone, Norton felt less confident playing Tite and having an OLB on the line rushing. Unfortunately, none of his DLine are very effective from the edge either and this led to ineffective rushes. Even when the front 4 did get through on their own, Cam easily escaped.

So the Tite front generated more effective pressures, more of them, and with fewer blitzers. At the start of the 4th, it was called 5 times in a row as Seattle forced New England's final punt of the game.

So why did they go away from it?

2 reasons:
Tite fronts don't go well with prevent defenses. And Irvin's injury meant that there was no one to play the blitzing LB role that fits with the Tite fronts.

Without him for the season, Seattle will have to find another way to call Tite, and to get to the QB.

Quick notes:
First attempt to look at EPA. EPA is from @pfref.
All charted myself, without All22, so likely to be some mistakes.
I was VERY liberal with what was a 'pressure'. My numbers are much higher than PFR's. Possibly closer to a DLine win rate.