Marshall is one of the few athletes that has "come out" as having Borderline Personality Disorder.
I think this scared Pete and John off after the Percy Harvin experience.
I've expressed the opinion that Harvin checks all the boxes for Borderline Personality Disorder (BPD), plus a side helping of Antisocial Personality Disorder, aka sociopath. I would bet money that the Seahawks had him evaluated and diagnosed, except that it's an unknowable proposition, short of Harvin himself "coming out". A team would never publicly "out" a player for this type of condition.
It's unfortunate that Seattle didn't pursue Marshall, because I believe he is a different type of BPD with lesser sociopathic behaviors in his past. I think he would have been a great fit in Seattle. I don't blame Pete and John for perhaps being gun-shy with BPD issues after the Harvin fiasco. Possibly Seattle not pursuing Marshall HARD had as much or more to do with Marshall's salary cap fit.
All things considered, pursuing a guy like Andre Johnson probably makes more sense for Seattle. No locker room issues, a great mentor for younger receivers, and probably a cap number of half or less of Marshall, plus *driven* to win a title at this point in his career. And probably very effective for Seattle, becoming our #1 guy, assuming there's still a bit left in the tank. Keeping my fingers crossed for an Andre Johnson acquisition by Seattle.