#No one saw this Mets dominance coming: ‘How did they do it?’

This was more of a coronation than a series. Four games that summed up the Mets’ stunning second-half run from also-ran to National League champions. It began with them considered the underdog to the young and powerful Cubs and ended with little doubt who was superior.

The finale of the 2015 NLCS was fitting to this one-sided series, the Mets storming out to a big early lead, Daniel Murphy going deep for the sixth straight game of his miraculous postseason and a wild celebration following an 8-3 victory at the front of the Wrigley Field mound that capped a stunning sweep.

“I’m standing there in the dugout in the ninth inning and I’m just looking at all the guys and thinking, ‘How did they do it?’ ” manager Terry Collins said after the Mets advanced to their first World Series in 15 years, since losing in five games to the Yankees.

“How did they keep it together? How did they stay focused?”

At one point in late July the Mets were just one game over .500. The lineup was offensively challenged, decimated by injuries. But then reinforcements came. General manager Sandy Alderson made a series of trades, bringing in Juan Uribe, Kelly Johnson and Yoenis Cespedes. Rookie Michael Conforto provided punch after a late July call-up and Travis d’Arnaud, Lucas Duda and David Wright returned from long injury absences.

The most important move, however, was the trade that wasn’t. After initially agreeing to send Wilmer Flores and Zack Wheeler to the Brewers for Carlos Gomez, the Mets backed out of the deal due to a problem with Gomez’s hip. Alderson then turned around and landed Cespedes from the Tigers just before the trade deadline for minor league prospects Michael Fulmer and Luis Cessa. Cespedes would key the Mets’ NL East title run, blasting 17 home runs and driving in 44 runs with a .942 OPS in 57 games down the stretch.

Still, the big stars of this postseason run were Murphy and the young fire-balling starting rotation. Matt Harvey, Noah Syndergaard and Jacob deGrom all turned in dominant outings to give the Mets a 3-0 series lead over the Cubs. Steven Matz delivered 4 2/3 innings of one-run ball in Game 4. Murphy’s NLDS heroics carried over and he was named the NLCS MVP after homering four times and batting .529.

“I’ll get a chance to tell people I played with Babe Ruth,” Curtis Granderson said of Murphy, who had seven homers and 11 RBIs in nine postseason games up to this point.

Duda delivered an early salvo in the clincher, a three-run, first-inning shot off Jason Hammel, and d’Arnaud followed with his own longball, giving the Mets a 4-0 lead before Matz had even delivered a pitch. Bartolo Colon came in for Matz with two outs in the fifth and delivered 1 1/3 scoreless frames. Addison Reed, Tyler Clippard and Jeurys Familia went the rest of the way as the Mets finished the series by outscoring the Cubs, 21-8.

“They did not let us up for air at any point,” Cubs manager Joe Maddon said. “Their domination of the early part of the game and their pitching was impressive.”