Chiefs quarterback Patrick Mahomes arrived in St. Joseph, Missouri, on a weekday in July, six months removed from winning his third Super Bowl and one month after the ring ceremony to celebrate it.

Yet as he stood in front of a campus dormitory, recapping the previous season, he actually uttered these words: “It wasn’t fun.”

Really. He said that. And if you followed the Chiefs closely, well, you probably understood. The offense had slogged its way through the regular season before turning it on in the playoffs, sidestepping one of the most difficult postseason routes in NFL history for a second straight title.

It’s one season later, and for the initial 15 weeks of it, the symmetry was perfectly evident — the Chiefs have never ranked worse in points (15) or yards (16) per game in the Mahomes tenure than they did this year. (The shutout loss Sunday, with the backups playing, didn’t help those rankings, though the backups played in the regular-season finale a year ago.)

But a funny thing happened 16 weeks into an 18-week season.

The Chiefs suddenly became the Chiefs again.

And Patrick Mahomes suddenly became Patrick Mahomes again.

But how?

How did the Chiefs transform, like the snap of a fingers, from looking as vulnerable as they ever have with Mahomes to returning to the top of the Super Bowl favorites sheet in Las Vegas?

It’s a multi-faceted journey, and let’s first understand its impact — because it’s a lot more than the eye test. The most expected points added (EPA) that Mahomes totaled in a single game this season came on Christmas Day in Pittsburgh, per data on Next Gen Stats. That was the last time we saw him play in the regular season.

The second-most EPA Mahomes totaled in a game this season came just four days before Christmas, in a win over the Texans — the second-to-last time we saw him in the regular season.

His best in Week 16. And then he one-upped it in Week 17.

What precipitated the change?

A lot.

It’s the players, for starters. The late-season return of Hollywood Brown from a sternoclavicular injury has made a real difference. He’s as talented as any receiver on the roster, and, amazingly, hasn’t shown rust despite missing four months.

The late-season surge from rookie Xavier Worthy is like a two-for-one packaged deal in the wide receiver room.

But we’ve mentioned the personnel. We’ve analyzed the impact. There’s more to it than personnel.

Such as the scheme. There are two other statistics that stand out besides the Mahomes EPA numbers — that supply a reason for those numbers, if you will. The first:

The quickest average time Mahomes has released the football in a game this season came in Week 17 against the Steelers. The second quickest came four days earlier against the Texans. Noticing the pattern, right?

The second stat: The highest percentage of play-action the Chiefs have used in a game this season came against the Steelers. You can probably fill in the blank by now, huh? The third-most play-action the Chiefs used in any game this year came against the Texans. Same pattern. Almost identical.

It’s the scheme, too.

Coach Andy Reid and offensive coordinator Matt Nagy just plain outwitted opposing defensive coordinators in back-to-back weeks with stuff they weren’t using all season — and two good d-coordinators, by the way. The Texans and Steelers have top-10 defenses and are even better against the pass than they are the run.

Perhaps the Chiefs instituted some changes because of the pressure those defensive lines consistently create — coupled with the makeshift offensive line that asked Joe Thuney to move from guard to tackle. They knew their game plan had to change. They experimented with whether the results would change too.

More play-action. But get rid of the ball quicker.

Game on.

And we should’ve seen it coming.

See, there’s a misconception about the way the Chiefs’ offense operates, particularly this season anyway. This idea that they’re built solely on Mahomes’ ability to extend plays — to buy more time — is backed by anecdotal evidence but contrasted by consistent results.

This year’s Chiefs offense is at its best when it’s in rhythm and on schedule. When it’s quick. When it’s decisive. Mahomes thrives in that environment, a setting that best takes advantage of his ability to release the ball through a variety of arm angles.

When he released the ball in less than 2 1/2 seconds this season, he posted a 105.6 passer rating, according to data tracked by PFF. But in passing attempts in which he used more than 2 1/2 seconds before the release, his passer rating dipped to 77.6.

That difference — 28 points — is the second-largest gap in football, behind only Pittsburgh’s Russell Wilson.

For certain, Mahomes’ ability to extend plays, often making something from nothing, provides the backdrop for the most what-the-hell-just-happened plays of his career. You can’t altogether lose that part of the offense.

It’s the essence of Mahomes’ magic.

It’s the identity of a three-time Super Bowl MVP.

But late — very late — in the season, the Chiefs moved away from requiring magic as part of the offensive formula. The first option can be the best option sometimes.

As a result, after leaning on their running game for the first half of the season, the Chiefs have figured out their passing game at a perfect time to figure it out. They’re a pass-first team again, because they should be a pass-first team again.

The quarterback, even with that improbable makeshift offensive line, looks comfortable again.

The offense is giving the ball to receivers in stride again.

It’s looked, well, fun again.