NEW YORK — It was almost touching to see Conan O’Brien look so tickled about his sudden rise in ratings. The departing host of “The Tonight Show” looked gratified, as if he had at last won the mass audience he believes he deserves.

People are riveted by the NBC debacle for reasons that have nothing to do with talent and everything to do with expectations. The Leno-O’Brien fracas is both shocking — an explosion of incivility that burns through late-night bonhomie — and also reassuring.

It turns out that the cliche that comics are angry, bitter people deep down is true.

NBC on Thursday confirmed it had reached a deal with O’Brien to walk away. And O’Brien, who is getting an estimated $32.5 million, is still using his last moments on the “Tonight” stage attacking the network. And that includes spending extravagantly on frills for the show, like the rights to use the Rolling Stones song “Satisfaction.”

Even the imperturbably jovial Jay Leno, who is getting what he wanted, namely “The Tonight Show” back, dropped his Everyman mask this week to aim a cross-network shot at David Letterman, who has mocked him and NBC unmercifully. “You know the best way to get Letterman to ignore you?” Leno said in his monologue on Wednesday. “Marry him.”

Unexpected vitriol

This normally doesn’t happen. Television in the reality-show era is a world of rudeness and disinhibition except on network late-night programs, where old-fashioned show business etiquette, the Johnny Carson model, still rules. In an era of the Internet and too much choice on cable, the traditional talk shows have lost their sovereignty — even mock-news programs like “The Daily Show with Jon Stewart” and “The Colbert Report” have siphoned away viewers. Classic late-night shows now distinguish themselves most by not being too distinctive.

However clownish, the late-night host is cool and self-contained, sending up the water-cooler follies of the day in a benevolent manner. Suddenly, Leno, O’Brien, Letterman and their ilk are the water-cooler folly, and they are neither removed nor benevolent. At times they have seemed as outraged and sanctimonious as the politicians, news anchors and movie stars they normally lampoon.

Leno and his peers will undoubtedly try to go back to normal once O’Brien is gone and his “Team CoCo” followers calm down, but the veneer of late-night niceness may be gone for good.

Letterman is an exception, of course. His comic style is laced with his peeves and personal grievances; when he lost “The Tonight Show” job to Leno in 1992 and moved to CBS the next year, he made a running joke of that setback and network executives, but after a while he mostly left Leno alone.

That ended almost as soon as NBC began its bizarre programming switcheroo, as the feeble ratings of Leno’s new 10 p.m. comedy show alarmed the network’s local affiliates. Letterman came down with a late-night version of posttraumatic stress disorder, reliving through O’Brien his own sense of ill treatment. His mockery of Leno has been savage — including high-pitched imitations of his rival’s voice — but he hasn’t let his allegiance to O’Brien totally cloud his own discontents. Noting O’Brien’s huge payout, Letterman said sourly, “You know, when I left NBC, all I got was a restraining order.”

Letterman’s barbs are some of the sharpest of the three, but they are not as unsettling because he has a long history of living his life onstage, notably when he told viewers he was being blackmailed over an affair with a staff member, and it turned out he wasn’t kidding.

Becoming a spectacle

Leno and O’Brien, on the other hand, keep their personal lives out of their comedy, trading instead on friendly facades — there is nothing dark or mysterious about them, or there wasn’t until now. Leno, who was magnanimous at first, has grown defensive and even somewhat surly, which clashes with his Teflon comic persona but is somewhat understandable: a jeering jury of his peers, including Jimmy Kimmel of ABC, portray him as a piggish diva who stole “The Tonight Show” after giving it to O’Brien.

And O’Brien, who began on a self-deprecating note, has turned more self-righteous in his monologues, blaming the network and Leno for taking back the show only seven months after he started. And his sense of betrayal is perhaps fanned by the followers who have held protests outside NBC headquarters at Rockefeller Center, as if the network is Myanmar and O’Brien the Daw Aung San Suu Kyi of late-night comedy.

All the comedians have been funny about their plight, but at the moment it’s their lack of humor that is the spectacle. Viewers are transfixed like schoolchildren watching their teachers break into a food fight — delighted, but also disoriented.