Nole won Wimbledon in his magic year, he won there because his level was insane, not because he is great on grass, in fact, playing "normal" as he did this year (which is great also) I can hardly imagine Novak winning a grass title again. He can even lost to Del Potro on grass, and we know DelPo is quite average on it.
Djokovic's 2011 grass level would not have been enough to take the tournament in many many other years. he just had the great fortune of not facing anyone playing insane grass court tennis as well as had the fantastic confidence
as you mention, there's a difference between playing well and with confidence and having a great type of game to go alongside a surface