Channing Dungey’s time as president of ABC was short. But it was certainly memorable — both for moves she made and for shockwaves she and her network attempted to absorb.

As the head of the network, Dungey made several canny decisions meant to reframe ABC as the default choice for Middle America. What was until recently a network organized around the dramatic brilliance of Shonda Rhimes and the razor wit of Kenya Barris was to become the network of folksy, plainspoken conservatives (“Roseanne”), sweetly aspirational music competition (“American Idol”) and pleasant uplift (“The Good Doctor”). But big bets tended to slightly underwhelm — the appetites and habits of the audience having changed since a show’s heyday, “American Idol” was a success but not a smash — or in the case of “Roseanne,” to blow up in all the wrong ways. And making matters worse, Dungey lost her network’s two signature creative forces, Rhimes and Barris, to Netflix.

Her departure makes it a clean sweep across the broadcast networks: Each has lost a top-level executive this year, with Robert Greenblatt stepping down from NBC, Gary Newman unable to come to an accord with Fox in its merger with Disney, and Leslie Moonves losing his place as chairman of CBS amid allegations of sexual misconduct. But Dungey’s story feels most illustrative of the challenges facing networks and their chiefs in an increasingly difficult landscape. The brevity of her tenure — nearly three years — makes it clear the job was something of a poisoned chalice. So too did the choices she was forced into, and choices that were made for her.

Dungey likely could have done more to nurture her network’s relationships with Rhimes and especially with Barris, who has spoken of feeling bruised over ABC’s risk-averse handling of a “Black-ish” episode addressing football players kneeling during the national anthem to protest police brutality. But there was no realistic way ABC could compete with the compensation offered the two creatives by Netflix. And in a climate short on reliable ratings draws, Dungey’s two series revivals brought little but grief. ABC shelled out massively for an only decently performing “Idol” and was delighted by the ratings of “Roseanne” — before watching its star implode with a racist barb on Twitter. A network not starved for hits would likely not have gone into business with Barr, known long before her show’s revival as a social-media troll; even at the peak of its success, the show was the most conditional of victories. In its iteration as “The Conners,” the series has come to feel like a concession to failure, an acknowledgment that ABC was compelled by panic into making a show it otherwise would never have.

It turns out Middle America is just like everyone else: Many, enrapt by Netflix and HBO Go and Fortnite, have fallen out of the habit of watching broadcast television nightly. That ABC can’t even get reliable ratings for its signature live event, the Academy Awards, signals just how much the ground shifted under the feet of Dungey and every other broadcast TV executive. Dungey’s place in history is earned in part by having lived through so much of it so quickly. She may well be remembered less for what she did than for what she presided over: a network in the moment that networks’ primacy conclusively fell away.