Op-Eds are not different than editorials. They are editorials. The term "Opposite from Editorials" is an antiquated term that the New York Times
admitted is antiquated and wishes to discontinue, and originally referenced the geographic position of the article in the newspaper and its relation to what was previously classified as 'editorials'.
Today Op-Ed is colloquially known as 'opinions and editorials' -
Covering Your Campus: A Guide for Student Newspapers
https://lmtimes.ca/glossary
In this case, however, the author of the article is affiliated to the publication. The author in question has had his own column in the New York Times for the last 20 years since 2003, so it can hardly be said that he is not affiliated with with the paper:
https://archive.nytimes.com/www.nytimes.com/ref/opinion/BROOKS-BIO.html?pagewanted=all
You already know this, and you already know that of course not every opinion piece that a newspaper publishes is meant to represent the newspaper's official opinion.
Since it is going through the editors, what is published are the positions of the newspaper. They won't publish my Flat Earth Dinosaur stuff, so they obviously are picking and choosing what they want to present and are policing the positions that they want you to think about. This argument that you can filter and select a selection of opinions for your newspaper and then pretend that it is not your selection is a ridiculous and flawed take. It obviously and directly is your selection that you are presenting to the public under your brand.
No, that's not the crux of the article; it's just one paragraph. The bulk of the article discusses, like I said, the creation of of an "elite" professional culture that left enough people feeling isolated and left behind to rally behind someone like Trump, who positioned himself as standing in opposition to that culture.
What you are describing there is some liberals trying to push beliefs onto people who don't really believe it, which is bad. This is evidenced by firing and canceling people who don't act a certain way. That makes liberals the 'bad guys', as stated in the article. The author's point is clearly that the movement is full of contradictions, close-mindedness, and derangement.
The author also further suggests that the above is why the liberals who have bought into the movement can't understand why Trump is not universally hated as a dictator and bad person.
As you undoubtedly already know (because otherwise I'm sure you wouldn't be putting so much focus on how liberal the author supposedly is), David Brooks is a conservative and not a disaffected liberal.
He has his own personal definition of conservative which involves taking many liberal positions and not backing any Republican candidate:
https://en.wikipedia.org/wiki/David_Brooks_(commentator)When asked what he thinks of charges that he's "not a real conservative" or "squishy", Brooks has said that "if you define conservative by support for the Republican candidate or the belief that tax cuts are the correct answer to all problems, I guess I don't fit that agenda. But I do think that I'm part of a long-standing conservative tradition that has to do with Edmund Burke ... and Alexander Hamilton."
On the same page he also says that he's actually in the "Democrat Party":
In December 2021, he wrote that he placed himself "on the rightward edge of the leftward tendency—in the more promising soil of the moderate wing of the Democratic Party."
In the NYT article in question he is clearly acting as a liberal/democrat and is criticizing the liberal movement. He is criticizing liberals from the position of a liberal.