Call me a feminist sentimentalist. After spending the first of what would be four years researching the ascent to TV news superstardom of Diane Sawyer, Katie Couric and Christiane Amanpour for my forthcoming book, The News Sorority, and discovering what these women were initially up against, I felt, in March 2010, like a hiker who’d vicariously reached a happy summit. Who’d have thunk it: Two out of the three 6:30 network solo anchors and one out of three Sunday news round-up anchors were female.

Three out of six. Half.

Five years before that, zero women had ever been in those roles. In early 2010, Christiane Amanpour had just been appointed the first female solo anchor of a modern network Sunday talk show (This Week). Katie Couric had been at CBS Evening News since September 2006, the first-ever 6:30 PM female solo anchor. After a rocky start modernizing the classic, if not ossified, format, Katie eventually earned respect – and affected the outcome of a Presidential election with her masterful 2008 interviews of Sarah Palin.

When Diane Sawyer rose to the anchor desk at ABC World News at the tail-end of 2009, it was the smoothest of the three ascendancies. The tone she set — serious and dignified but empathic; unerringly hard-news-minded yet wisely reflecting a sense of heartland America’s bread-and-butter concerns — is the one she has carried on since. Her ascendance didn’t say: NEWS FLASH! FEMALE PERSON IN CHAIR! She was just what the doctor ordered for relatively conservative 6:30 PM.

When ABC first announced that she’d take over from Charlie Gibson, World News’s producer Jon Banner said, “There was nobody more qualified to step into that chair, and in some cases she was [also] probably more qualified years beforehand.” Sawyer, a famously hard-working perfectionist throughout her then-28-year-long national network career had seemed, to many media watchers, an even more obvious choice than Gibson, when he snared the post in 2006.

And when she left behind her ten-year tenure at Good Morning, America, Diane attacked the task with head-spinning vigor and variety: flying to Copenhagen to interview Mahmoud Ahmadinejad; then back to New York to open her broadcast with news of a Christmas “miracle” of community do-gooding at a Vermont church; then off to Afghanistan, a foray she interrupted to take three planes and a tiny helicopter to Haiti when the earthquake struck. (With no hotels available, she and her crew slept in a baggage cart that first night.) All this was in her first three weeks as anchor. The gauntlet she threw down — to always be on top of the news, wherever it was — was something she never let up.

But things changed from that heady moment in early 2010. In a decision that was not hers, Katie left CBS Evening News in May 2011. Christiane’s imminent dismissal from This Week was announced seven months later. (She was warmly welcomed “home” to CNN, but to a less visible position to U.S. viewers than she’d previously occupied.)

Diane was the last woman standing.

And stand she did — strong and tall. She alternated her calm, exacting hard-news reporting with her public-service-mission’d “Made In America.” She was the only anchor to travel to still-endangered Japan when the earthquake and tsunami struck. And—possibly most meaningful to the social-issues reporter she had become in the ’90s at PrimeTime, and to the Methodist Youth Association Diane from Louisville her best friends know — she did a series of award-winning specials on endangered children: in Camden, New Jersey; on a South Dakota Indian reservation; in gang-saturated Chicago; and in the Appalachia of her parents’ hardscrabble childhoods.

But her news program consistently lagged behind NBC’s Nightly News with Brian Williams. When CBS Evening News enjoyed a ratings uptick after Katie was replaced by Scott Pelley, a phrase that had been whispered during Katie’s years at CBS was uttered full-volume: 6:30 viewers would watch “any white man in a chair” before they’d watch a woman.

I started hearing that Diane would be eased out and replaced by the less expensive David Muir two years ago.

Last summer, exciting news appeared in the New York Times.: “…World News with Diane Sawyer bested NBC Nightly News With Brian Williams among 25-to-54-year-old-viewers last week, ending [Williams’ and NBC’s] winning streak of almost five years.” But the article dropped a second shoe with an ironic thud: “The victory was shared by Ms. Sawyer and one of her regular fill-ins, David Muir… because [emphasis is mine] Mr. Muir substituted for Ms. Sawyer…the same three nights…that ABC beat NBC in the all-important demographic.“

This month, Diane Sawyer and ABC World News again eclipsed NBC and Williams in that prized demographic. Yet yesterday ABC announced that Diane will step down as anchor in August, to be replaced by Muir, with George Stephanopoulos lead-anchoring on election nights. (Small pause to enjoy the fact that two men have to do the job Diane did by herself.)

Diane will continue her specials, like the sit-down she had with Hillary Clinton recently, and her social-issues pieces. With Barbara Walters retired, she’ll have a whole ABC-wide field all to herself.

So, rationally, there’s no reason to mourn this news, nor to disbelieve the long-heard buzz that Jean Sawyer Hayes’s and Mike Nichols’ vulnerable health are reasons she might want to take things easier — anyone who knows Diane knows how crucial both her husband and her mother are to her.

But still. In March 2010, three out of six.

Now, August 2014, back to zero.

From the Medieval days of town criers to Walter Cronkite’s dabbed tear at John F. Kennedy’s death to the horrendous morning of September 11, 2001, the deliverer of our news has filled an irreplaceable role, as one who unites us. Let’s not hope for any more crises, but let’s remember that on September 11 it was largely two women — Diane and Katie — who rigorously, compassionately gave us the shocking news as it unfolded. In these days when our country sorely needs some unity, it would be nice and maybe even necessary to have a female sensibility— a woman— in that role again.

UPDATE: A friend at ABC says of the reason for Diane’s stepping down: “She wants the flexibility to tackle big projects full-time. So it’s not true that this is about anything else. Mike is great and starting a new project. Her mom is fine.”

Sheila Weller is a contributor to Vanity Fair, The New York Times Book Review, and Glamour, and the author of the New York Times bestseller Girls Like Us. Her forthcoming book, The News Sorority: Diane Sawyer, Katie Couric, Christiane Amanpour—and the (Ongoing, Imperfect, Complicated) Triumph of Women in TV News, will be published in September by The Penguin Press.

Contact us at letters@time.com.