http://www.atpworldtour.com/en/news/miami-2017-final-federer-nadal
What is there to say but that we have a phenomenon in play where a supposedly over the hill athlete that had been written off by tennis analysts many times is still contending for the top tier of tennis. His win in Australia and now in Miami says that he is in top form and if he continues as he is with disciplined use of his energy and time to avoid overplaying he may continue this streak.
This performance is a great example of what getting a rest and limiting play can do for you. Overplaying is one of the worst things that a tennis player can do to reduced their performance and long term viability by risking injuries.