When 200 Google workers and their allies held a rally in San Francisco last month, their stated purpose was fighting alleged retaliation by company leadership against employees who spoke out against the search giant. But one protester held up a poster board sign that encapsulated a broader battle cry: "Save our open culture."

The search giant's famously freewheeling demeanor has eroded over the recent past as Google grew more and more corporate. On Tuesday, its future fell into greater question after co-founders Larry Page and Sergey Brin dropped bombshell news: The iconic pair said they would be stepping aside as leaders of Google parent company Alphabet, leaving Google CEO Sundar Pichai in charge of the entire show.

Founders are always closely identified with the cultures of their companies. Steve Jobs cemented Apple's reputation for perfectionism. Jeff Bezos created Amazon's customer-centric mission. At Google, Page and Brin are human manifestations of -- and direct links to -- a romanticized open culture that fostered creativity, even if it had no immediate benefit for the company.

Page and Brin grounded Google in an ethos that promoted internal transparency, even if it seemed from the outside to be as opaque as the company's search algorithm. Employees were encouraged to check out projects their coworkers were developing, something unheard of in secretive Silicon Valley. By corporate America's yardstick, the Google environment was borderline anarchic -- employees could spend 20% of their time working on a side project, in hopes it could become Google's next big thing. 

The co-founders -- friends from Stanford University who built their company in a garage -- will remain board members. But some employees already worry that with Page and Brin officially out of the day-to-day picture, the company will feel rudderless in what are definitely turbulent times. With Page and Brin gone, they wonder, who will protect Google's culture?

"Some had seriously hoped Sergey and Larry would step in and fix Google," employee organizers at Google tweeted. "Instead of righting the sinking ship, they jumped ship." 

We kid, but here's the thing: some had seriously hoped Sergey and Larry would step in and fix Google. Instead of righting the sinking ship, they jumped ship. Only workers like the #thanksgivingfour will fix Google. https://t.co/HYf5pft6Gy

— Google Walkout For Real Change (@GoogleWalkout) December 3, 2019

Google faces the greatest challenges to its culture in its 21-year history. Tensions continue to escalate between Google management and rank-and-file employees. Activists within the search giant have protested decisions by leadership, including the signing of an artificial intelligence contract with the Pentagon and Google's work in China. Most notably, 20,000 employees walked out of their offices last November to protest leadership's handling of sexual assault allegations.

As if to highlight the growing conflict over Google's open culture, four former employees said they planned to file charges of unfair labor practices against the company on the same day Brin and Page announced they're stepping aside. The former employees, who were fired in November, accused Google of sacking them for "engaging in protected labor organizing." Google said the employees were fired for violating data security policies, not organizing.

At last month's rally, two of the fired workers, Rebecca Rivers and Laurence Berland, gave speeches condemning management's reining in of the culture. The two were placed on administrative leave earlier for accessing documents and calendar information that Google says was outside the scope of their jobs.

Still, Google's internal response to the firings indicated that commitment to the culture has already waned. "This is not how Google's open culture works or was ever intended to work," Google's security team told employees in a memo about the firings. 

'Ben and Jerry'

In some ways, the change in leadership is both monumental and uneventful. Page and Brin have long been no-shows inside the company, employees and former employees say. The pair used to be mainstays at Google's famed TGIF meetings, weekly all-company gatherings and one of Google's most time-honored traditions. 

Page and Brin, though, retreated from the spotlight not long after the Google walkout last November. They skipped every TGIF this year except one in late May. For longtime Google employees who remember the early days, seeing Page and Brin on stage sparked a pang of yearning. "People still have this old-time fondness for them," said one person who watched the meeting. "They're like Ben and Jerry."

For many at Google, the death knell for Google's open culture came last month, when Pichai said Google would scale back TGIF to once a month, rather than once a week or biweekly. Pichai said he was making the gatherings less frequent because of a "coordinated effort" to leak comments made at the internal meetings. Instead of being open forums and sounding boards, TGIFs will now be more product-focused. 

"TGIF wasn't perfect," Berland, one of the fired employees, said at last month's rally. "But at least we got the chance to ask the questions."

Going forward, Pichai could make more changes. "Every CEO wants to put their own stamp on the way they lead, so this is an area to watch as he shifts his role to CEO," said Tim Bajarin, president of Creative Strategies, though he said he doesn't see big cultural changes in the short term.

Before Tuesday's announcement, some employees had hoped the co-founders would take more active roles again. When Google workers held a sit-in in May to protest a "culture of retaliation" against workers who spoke out against the company, they called on Page -- not Pichai -- to step in. They urged him to "immediately and publicly address the Walkout's demands, and recommit Google to meeting them."

The leadership change means Page and Brin's day-to-day absence has been cemented.

"Seems like it's already been the case for a while," a Google employee, who asked to remain unidentified for fear of retribution, told me on Tuesday. "Just now it's official."

CNET's Queenie Wong contributed to this report.