The Mets success is partially due to their exceptional rotation led by the 42 year old Bartolo Colon who is still pitching like he did in his prime. He and A-Rod are the only active players who have been all-stars in each of the past 3 decades (90s, 00s, and 10s). Colon is backed up by four pitchers still in the prime of their career. Jacob deGrom, who was last season's rookie of the year and has a 0.93 ERA this season and 2.48 in his career. After that they have Matt Harvey who like the Marlin's Jose Fernandez could have been one of the best pitchers in baseball last season if not for Tommy John surgery. Then Jon Niese, and Dillon Gee who have been back end rocks or the mets in seasons past. This is all without Zack Wheeler who is recovering from Tommy John. The Mets have produced numerous strong young pitchers over the years, and this is finally paying off for them.
One huge piece of the Mets success is first baseman Lucas Duda last season he was one of the most undervalued players in the majors. In a nine inning game a lineup of just Lucas Duda would score an average of 6.0 runs and it would take the opponent 167 pitches to finish the game. This year Duda has performed at this same level and been the most valuable player on the mets.
The mets also owe much of their success to the bat of Michael Cuddyer, Wilmer Flores, and the fill in work of Eric Campbell for the injured David Wright who has an OBP of .394.