It may seem surprising that some people care enough about the Rockefeller Center Christmas tree — whose most recent incarnation, all 90-plus feet and 50,000 lights of it, was lit Wednesday night — to brave jostling crowds and low temperatures to see its unveiling. Why turn on the TV to watch a somewhat religious tradition writ large, plus hours of advertisements and strained Christmas-themed music to get to the singular light switch moment?

One answer as to why the tree lighting continues to be such an annual rite, beyond long-standing Christian conventions and generally good ad revenue, lies in its origins in 1931, before the center was even completed.

Just before Christmas that year, workers building the new Rockefeller Center gathered under the first Rockefeller Center tree, celebrating the holiday and the only ray of economic light in the city during the Great Depression.

The Depression hit NYC particularly hard. Unemployment in the region reached 25 percent, but things were even worse in the construction industry, says Daniel Okrent, author of “Great Fortune: The Epic of Rockefeller Center.” Sixty-four percent of construction workers were out of a job.

Okrent says there was no major private development in the 15 years between the Empire State’s completion in 1931 and the Columbia Pictures Building in 1946. “The only one was Rockefeller Center.”

It was an era when those out of work fed themselves on “tomato soup” made from ketchup and hot water, Okrent notes in “Great Fortune.”

In that historical moment, John D. Rockefeller Jr., son of the wealthy oil baron, donated a million dollars to the Emergency Employment Committee charity, but had perhaps an even greater economic effect by sticking to his plan to build a town square and commercial center in what had been a swathe of dilapidated brownstones. Tens of thousands were put to work.

It was easy enough for a man with a fortune like Rockefeller’s to get a good reputation in this way — he was even praised by labor leaders in 1932 for “only” reducing wages by 15 percent, according to “Great Fortune.” But other business leaders were much less generous. Workers felt lucky to have jobs demolishing the area around the new Rockefeller Center and building it up again, as indicated in a picture taken Dec. 24, 1931 showing workmen gathered around a 20-foot Balsam fir Christmas tree on the site, waiting for their wages and bonuses for their work.

The men decorated the tree with paper garlands and strings, and also “the tin foil ends of blasting caps,” says Christine Roussel, of the Rockefeller Center Archive. The decoration came from the dynamite.

Roussel and some later news accounts say the workmen purchased the tree themselves because “they appreciated their jobs, they appreciated Christmas.”

Okrent says it’s not historically clear who actually paid for the tree, though the workmen appear to have decorated it. And they were certainly happy to be employed, something to celebrate that season.

This season, the holidays seemed to jump upon us quickly, with so much energy being spent fretting over and processing the presidential election of 21st century wealthy New York businessman Donald Trump, who relied on some of the same economic anxieties that plagued the country in a different time of turmoil to launch him to power.

Trump, whose aversion to philanthropy has been well documented, is a far cry from the middle Rockefeller, who cherished the biblical quote “unto he who much is given, much shall be required,” according to “Great Fortune.”

Nor are his buildings as monumental or as generally useful as Rockefeller Center turned out to be.

Many Trump properties were built as “enclosed fortresses” walled off from the city, says Okrent, as opposed to the “great ornament” of Rockefeller Center — lively and crowded around the skating rink and the tree, with decorated promenades toward the avenues.

Those will be filled throughout the holiday season with visitors and New Yorkers. It’s unlikely many will be drawn by knowledge of Rockefeller Jr.’s early 20th century civic mindedness. But those acts laid the groundwork for a cheerful space and night, bad music be damned.