It's not baffling to me at all. Russ turned his back on the fan base. He didn't want to play in Seattle any more. He looked at all the love he got from his adopted home and the best fans in the NFL, and said, I don't care about any of that. (Not one Seattle radio host or journalist blamed Russ for that SB interception. After throwing 4 in the NFC championship game. In any other place, he would have gotten a lot more blame.)
What Russ did was worse than A-Rod because you expect a player to get as much money as you can. Texas gave him a lot more than the Mariners could pay. Russ could have had the same money he got in Denver here. It wasn't Ken Griffey because he wasn't going home for sentimental reasons. It was worse than even LeBron leaving Cleveland because LeBron wanted to win a championship and the Cavaliers at that time were a horribly mismanaged franchise. Russ already won a Super Bowl in Seattle, and it wasn't like the Seahawks were perennial losers. And LeBron said he would go back one day, and he did.
What Russ did was very unusual--very few franchise quarterbacks choose to leave. The ones that do leave, did under very unusual circumstances: Brady, Manning, Favre. They didn't force themselves out with threats. And for what? Denver is that great of an organization? So he can have his own office and hire his own quarterback coach? So that he doesn't have to be coached any more?
And it wasn't just this year, but the last several years of his bullshit, complaining about the coaches, his offensive line, threatening not to re-sign and demanding to be traded. He and his agent making a big deal about Schneider going to scout Josh Allen, or being interested in other college QBs--isn't that what GMs are supposed to do? Going on the Rich Eisen show and basically saying, "It's me or Pete." He created the three-ring circus, all for the purpose of forcing his way out of Seattle to a place of his choice.
What he did was a big F-you to Seattle, and so, of course, it's not at all baffling that the fans are pissed and don't wish him well. It's funny that a guy so concerned with his image didn't see this coming.