I expected this. His "standing up for Buffalo" speech was a last ditch effort to save his job.
McDermott did a lot to change the culture in Buffalo, but last year's AFC championship loss to KC was telling. They punched KC in the mouth in the regular season, but in the playoffs, they played to not lose. And that's how you lose.
The expectations might have been unfair this year considering how many key players had been lost, but clearly they feel some urgency to bring in a guy who can take their generational QB all the way and they no longer view McDermott as that guy. Harbaugh should have waited a bit longer.