And nobody ever said there wasn't a single case of a head coach, or other coach immediately walking into another head coaching gig either. The point was only that it wasn't a normal thing, and therefore the OP isn't making the point he suggests.
Frankly I didn't immediately think of Eberflus either. It took a minute or two of thinking about your comment before it dawned on me. As for him turning down the DC job in Dallas, the reports, as I recall, were that he was too close to Marinelli to feel right about being the reason Marinelli got demoted. In any case, I can't think of anyone else under Garrett that improved his situation, so I agree with your general point.
As for the pattern, I don't disagree, but my point was only that the pattern is normal with fired coaches rather than a commentary on the Cowboy coaches in particualar.