Yes you ignored the fact that City had took their foot off the pedal and as for why he played better than Fellaini? Well he hadn't been on 60 minutes already and hadn't played in midweek and was operating in a 3 which gave him the freedom neither Fellaini or Carrick had, there ya go.
No, I didn't ignore that fact, it was obvious they weren't playing with high intensity as they were in first half.
What freedom? That wasn't really midfield three, Fellaini was playing almost as second striker when he was introduced, so looking by positions, nothing changed too much in second half, except for different players playing in same positions. City even brought Milner and Garcia in second half to make them stronger in midfield in second half.