Current and former colleagues of Mr. Rusbridger’s, who acknowledged criticism of his business decisions, characterized him as a brilliant journalist — not to mention a talented pianist, an affinity he explored in a 2013 book — and nearly universally declined to discuss his departure for attribution, describing it as a sad way to end his affiliation with the institution.

Mr. Rusbridger, who was born in Zambia and graduated from the University of Cambridge in 1976 with a degree in English, started as a journalist at The Cambridge Evening News. He joined The Guardian in 1979, and in 1988 became an editor there. In 1994, he was promoted to deputy editor, before taking over the next year as editor in chief, a position he held until his departure last spring.

Cerebral and academic, with often unruly hair, Mr. Rusbridger had an inner steel that won him admiration and devotion. Early in his career at The Guardian, Mr. Rusbridger led the newspaper’s tenacious investigation of what became known as the cash-for-questions scandal in Parliament, which contributed to the fall of the Conservative government of Prime Minister John Major in 1997. Mr. Rusbridger stared down a libel suit against the newspaper by a powerful former minister involved in the scandal, Jonathan Aitken, who was ultimately jailed for perjury. In the hypercompetitive and partisan world of British journalism, Mr. Rusbridger was sometimes a lonely figure, often more admired in the United States than among his rivals at home.

As Mr. Rusbridger’s vision for the newsroom played out, the strategy appeared to have the full support of the top brass. Shortly after Mr. Rusbridger retired in 2015, Mr. Pemsel, the chief executive, said he was “hugely excited at the prospect of managing the next phase of growth at The Guardian, building on our international audience, capitalizing on the many commercial and digital opportunities.” Around that time, another top executive said the company’s finances had been good that year.

Then the bottom fell out. Print advertising cratered, and expected digital money never materialized.

Support for Mr. Rusbridger suddenly shifted, as he was cast as a negligent manager who had saddled the paper with a slew of problems. Janine Gibson, a favorite of Mr. Rusbridger’s who lost out in the race to succeed him, left with other senior Guardian journalists, further shifting the way his legacy was viewed in the newsroom. In January, Mr. Rusbridger’s choice as The Guardian’s opinion editor, Jonathan Freedland, stepped down in what was seen as a leftward shift in the organization’s editorial stance. And Ms. Viner’s plans for the newsroom seemed increasingly at odds with Mr. Rusbridger’s, making the idea that he would soon return, as essentially her boss, increasingly unsavory.

The negative sentiment started to rise in recent months, as several news media reports detailed a rising tide of internal discord, quoting high-ranking insiders who placed the blame for the company’s woes on Mr. Rusbridger’s policies and what they saw as his intractability. A critical article in Prospect Magazine took aim at Mr. Rusbridger’s decisions to “lavish money on new presses and delightful new offices.” It prompted Mr. Rusbridger to strike back, defending the move to make a “significant investment in digital today” in the hope of having a “sustainable business tomorrow.”