During Andy Lack’s first tour of duty leading NBC News, he helped “Dateline” bounce back from a dark era in which producers admitted to manipulating elements of an investigative report on General Motors, and expanded the hours of the “Today” morning franchise, and ratings success followed. None of that prepared him for what lay in wait during his second time at the news unit’s helm.

Lack, who is stepping down from NBCUniversal earlier than previously expected under a new reorganization set in motion by new CEO Jeff Shell, has been under scrutiny almost from the time he returned to NBCU in 2015. He joined the Comcast-owned media conglomerate while it was in the midst of a public-relations maelstrom around former “NBC Nightly News” anchor Brian Williams, and quickly moved through several other periods of tumult.

Lack, a colorful executive who has never been shy about experimenting with new concepts, was among the NBCU executives who wooed Megyn Kelly to NBCU from Fox News Channel, giving her two ill-fated programs and a massive multi-million dollar payout. He weathered criticism after former “Today” co-anchor Matt Lauer was fired from the network after allegations of sexual harassment surfaced. He had to contend with a roiled employee base and further opprobrium after NBC News allowed former MSNBC host and reporter Ronan Farrow to take his work looking into harassment allegations made against disgraced movie mogul Harvey Weinstein, which was started at NBC News, to a rival news operation, where its publication helped bring Weinstein to justice. Farrow, who wrote a 2019 book, “Catch & Kill,” about his time at NBC News, alleged executives there sought to obstruct his efforts  – claims NBC News has dismissed several times. Lack’s personal life and conduct at past jobs became fodder for press investigations.

The Lauer ouster and the swirl of details contained in the Farrow book sparked concern internally and spurred activist organizations to call upon NBCU’s parent, Comcast, to make changes at NBC News.

NBCUniversal investigated the news division in the wake of the Lauer firing. A report prepared by the company that was released in May of 2018 and greeted with some degree of skepticism said managers at the company’s “Today” show and at NBC News had no knowledge of inappropriate behavior by the star anchor prior to his dismissal in November.

Critics charged Lack didn’t heed the new rules of social interaction called for by movements like Time’s Up and #MeToo. His supporters noted he kept focus on the business of news at NBCUniversal, lending new momentum to MSNBC after a period of fallow ratings; pushing NBC News into the digital era, with new content for Snapchat, Quibi and a recently-launched in-house streaming-video outlet; and expanding the company overseas. A move to launch a global news network based in London was recently delayed due to the effects of the coronavirus pandemic.

Throughout his tenure, Lack enjoyed the support of Steve Burke, the company’s previous CEO, who accepted some of the blame for the NBC’s failure to turn Kelly into a success. “In hindsight we shouldn’t have done it,” Burke told Variety in 2019. “But it wasn’t Andy going off rogue.” Burke would continue to support Lack during his tenure, though in a re-organization of the company set last year, NBC News was placed under the oversight of an executive placed over Lack.

That defense rankled activists and others. “Andrew Lack is stepping down, after public protests calling for leadership change and a unionization effort within the company demanding more transparency about harassment issues there,” said Farrow via Twitter on Monday. “Grateful to the sources who spoke.”

Cesar Conde, an executive whose chief role in recent years has been overseeing NBCU’s international operations and its Spanish-language Telemundo network, will take over the company’s news operations – with a wider purview. Lack, who had oversight of CNBC during his first tenure, returned to the company to find CNBC’s president, Mark Hoffman, had his own line of reporting to NBCU’s  Burke. Under the new CEO’s plan, CNBC will become part of a larger corporate division that houses the company’s news operations.

NBCU declined to make Lack or Conde available for comment.

The installation of Conde in the news role interrupts a plan of succession that many expected to be completed by the end of the year. Under plans previously articulated by NBCU, Lack was expected to leave his role after the 2020 election. NBC News President Oppenheim was seen as his likely replacement.  One person familiar with the NBC News newsroom said some staffers had expressed hope after learning of the corporate changes that the news division might chart a period of calm under new management.

Unfortunately, there is still a chance for chaos in days to come. Staffers are worried about the potential for layoffs, according to another person familiar with the news division. The integration of CNBC into the NBC News and MSNBC operations will no doubt result in overlap of personnel behind the scenes and also on camera. Both news units have been growing their digital operations, and hiring reporters to cover such topics as media, politics and technology. An NBC News spokesman declined to comment on the potential for staff reductions.

Elizabeth Wagmeister and Ramin Setoodeh contributed to this report.