Because Eric Bienemy.
Bienemy had the OC title under Andy Reid, but couldn't get head coach consideration because no one knew whether he was any good or if Reid was the reason for the offensive success in KC. He had to take a job with the Commanders and prove that he could be a successful playcaller. And he failed.
Seattle has three very good receivers (well, two if Lockett retires), three very good RBs and yes, a good QB. At least any OC worth his salt is going to look at Geno's physical skills and figure that he can get the most from him.
Also, Seattle has proven that the team will spend money to put a quality product on the field. And Seattle is, with one game to go, a single game out of first place. Yes, tiebreakers etc etc. The point is, despite how much the offense struggled, the team isn't a shitshow, has an up and coming head coach, has a defense that has massively improved over the year, and if the offense had been even decent in even ONE of our losses we'd be playing for the division championship this weekend.
Lafleur is young and not going anywhere. If Stenovich doesn't want to compete for an OC job somewhere, then I wouldn't want him. He might not leave after this year, but he isn't going to stay forever. Show me a better situation with an OC vacancy.