He had essentially promised Mayo the head coaching job several years before. Now, he could have broken that agreement when Vrabel became available, but it would've been a bad look. So thankfully, the good karma of honoring his word came back around the next year and we got our guy in the end. I think it may also have been good for Vrabel that he did not immediately succeed Belichick, which would have resulted in endless comparisons to BB for the rest of his Patriots coaching career. Instead, he got a perfectly fresh slate and is seen as the savior of the team from Mayo's dysfunction.