Both Carrick and Ole were students of the game when they were playing. Carrick learned the coaching stuff from some of the greatest managers of all time, including SAF, VG, and Jose while playing/working for them.
But, obviously, doing it for United and other clubs is not the same. It is like players in that sense. So I'm not surprised he's doing so well now somewhere else, and I'm not surprised he (and the other guy) didn't do so well at United as coaching staff. Even if they have another chance as managers, they may never do it at United.