The WJM-TV newsroom is in mourning.

Betty White’s death on Dec. 31 marked the sixth major figure from “The Mary Tyler Moore Show” to pass in 2021. Actors Cloris Leachman, Gavin MacLeod, Ed Asner , series co-creator Allan Burns and director Jay Sandrich also died during the year that just ended.

The coincidental timing of the losses of these legends underscores the passage of time for the network television business. “Mary Tyler Moore,” “All in the Family,” “MASH” and other early 1970s shows ushered in the era of big ensemble comedy hits destined to endure as classics of the form. TV historian Tim Brooks has dubbed this period the “relevance era,” representing a backlash to the fantasy escapism of 1960s comedy hits such as “Bewitched” and “I Dream of Jeannie.”

“Mary Tyler Moore” was endowed from the start with a powerhouse cast, most of whom were also blessed with powerhouse genes.

White came within three weeks of celebrating her 100th birthday. Leachman and MacLeod both died at 94. Asner was 91. Sandrich, the director who helmed most of “Mary Tyler Moore’s” 168 episodes, was 89 when he died in September. Burns, a much-respected showrunner and comedy writer, died last January at 85. “Mary Tyler Moore’s” titular star died at 80 in 2017; Ted Knight was the first of the show’s core cast members to pass, at age 62 in 1986.

As massive as the television industry is today, network television in its modern form is only now getting to the age of seeing its longest-lived practitioners die after reaching their 80s and 90s. “Mary Tyler Moore” ran for seven seasons on CBS from 1970-1977 and remains a cultural touchstone.

“It’s a testament to their collaboration and their talents that even all these years later, all of them have been mourned as TV legends,” said Paula Bernstein, author of recent books “Love Is All Around and Other Lessons We’ve Learned From The Mary Tyler Moore Show” and “How to Be Golden: Lessons We Can Learn From Betty White.” “My mother in her 80s and my daughters who are teenagers all know the characters and they continue to resonate.”

James L. Brooks, co-creator and showrunner of “Mary Tyler Moore,” told Variety that the loss of so many collaborators made for a hard year but he emphasized that he mourned them as individuals and treasured collaborators.

“I think of each one of them specifically,” Brooks said. “I don’t think of this as a list.”

Brooks recalled White’s impact on “Mary Tyler Moore” when she joined the cast at the start of Season 4 in 1973. She was supposed to have a one-off guest shot, but White was so good in the role of the lascivious schemer Sue Ann Nevins that the character quickly became a series regular.

“She was a writer’s dream,” Brooks said. “She was just a godsend to the series when it happened. She relished the part and the part relished her.”

(Pictured clockwise from top left: “Mary Tyler Moore Show” stars Ted Knight, Gavin MacLeod, Ed Asner, Mary Tyler Moore, Georgia Engel and Betty White)

Clarification: This story has been updated to include the death of a sixth major figure from “The Mary Tyler Moore Show,” series co-creator Allan Burns, in January 2021.