Fed's level improved dramatically from the Masters Cup 2003, it was a shock quite like Djokovic's 2011, except that it kept on lasting for longer.
Meanwhile some of these players had problems.
And to say Fed's opponents choked is being biased to me.
I can do the same with Novak's great run: at 2011 AO he faced Murray who is a mental midget and always loses GS finals, at the USO Fed choked 2 match points, Nadal had him on the ropes at 4-2 in the fifth at the AO 2012 but choked it badly missing a backhand pass with all the court open. Nole's won cause he faced mental midgets or players who choked badly against him.
You see how it can be easy?