Back in 2016, a colleague handed Donald F. McGahn II, then a top legal adviser to the presidential candidate Donald J. Trump, an appeals court opinion that eloquently and powerfully echoed much of what Mr. McGahn saw as the evils of an out-of-control federal bureaucracy.

The opinion from the Denver-based appeals court by the relatively unknown Judge Neil M. Gorsuch suggested it might be time for federal courts to confront the “behemoth” of a longstanding precedent conferring substantial regulatory power on federal officials.

One month later, Mr. McGahn placed Judge Gorsuch on Mr. Trump’s list of potential Supreme Court nominees should he be elected.

Four months later, he was President Trump’s first nominee to the high court.

And over the past week, Justice Gorsuch wrote for the conservative majority on the Supreme Court that made sure the behemoth was slain.

While much of the attention to the conservative-dominated court has been about the sweeping decisions it has made to roll back abortion rights and now greatly expand presidential immunity, that was never the main goal for the architects of the effort to pull the judiciary to the right.

For those who led the drive to place Justice Gorsuch and two other conservatives on the court during the Trump administration, a sweeping series of rulings by the Supreme Court this year that shrank the power of federal agencies was the true victory. Their longtime target, the so-called administrative state, has been beaten back with the overturning of the 40-year-old Chevron doctrine and a flurry of other decisions aimed at reining in federal government reach — just as they envisioned it.