Ted Turner, who died on Wednesday aged 87, was many things – a philanthropist, a conservationist, the one-time husband of movie star Jane Fonda, a yachtsman and the owner of the Atlanta Braves and the Atlanta Hawks.

He thought big and lived large.

The phrase “make no small plans, they have no magic to stir men’s blood” is attributed to the architect Daniel Burnham but it might as well have been tattooed on Turner’s soul.

But, with all his accomplishments, surely his most notable legacy will be the way he changed the news media forever by founding CNN in 1980.

He himself called it the greatest achievement of his life, according to CNN’s obituary. The 24-hour news network brought the world into people’s living rooms, and eventually prompted imitators, from Fox News to MSNBC and beyond.

The cable news network he founded has been far from perfect, too often descending into chattering panels of experts and contentious arguments designed to fill the relentless all-day/all-night news cycle. But it has been overall a serious news provider with a global staff of principled and talented journalists.

“He was the original,” the iconic CNN journalist Christiane Amanpour said on air shortly after Turner’s death. “He made us all strive for his vision of a better world.”

But Turner’s original vision is under serious threat these days, as CNN’s parent company Warner Bros Discovery, prepares to come under new management. It’s the same new management that has turned another storied news organization, CBS News, into a diminished and politicized version of what it once was.

Once CBS News came under the sway of the uber-rich, Trump-friendly Ellison family, its long-held editorial independence began to atrophy.

David Ellison (son of the Oracle founder Larry Ellison, one of the world’s wealthiest people) is the CEO of Paramount Skydance. That mega-media company is set to own CNN’s parent, after its massive merger bid was approved by shareholders.

A competing plan from Netflix would have spun off CNN and probably protected its independence better. But with the help of the Trump administration, Paramount has prevailed.

Now, legitimate fear has set in that the Ellisons will do to CNN what they’ve done to CBS News. David Ellison installed as top editor Bari Weiss, a neophyte in TV news with strong political beliefs that, by many accounts, have made their way into the newsroom. And he appointed a conservative policy wonk with no real journalism background as the news department’s ombudsman.

David Ellison claims that editorial independence will continue at CNN, but if the past is prologue, I wouldn’t bet on it. And that will thrill President Trump who has been a harsh critic of CNN for years, deeming it woke, leftist and unfair to him, though there’s little evidence of that. The network, if anything, bends over backwards to represent various points of view.

Turner, I believe, wouldn’t want to see control of CNN change in this way.

He opposed the concentration of media ownership – the near-monopoly structure that now plagues our information ecosystem by stamping out all but the largest and concentrating too much power in too few hands.

“When you lose small businesses, you lose big ideas,” Turner wrote in a 2004 essay for Washington Monthly. But, he wrote, the federal government protects and fosters media consolidation, and hurts upstarts like he once was. The magazine republished Turner’s article on Wednesday, titled Ted Turner’s Beef with Big Media.

Turner’s legacy is complicated. For one thing, he championed editorial freedom but ran into criticism from his first star hire, Daniel Schorr, who frequently complained in the old days about the notion of CNN’s news features, claiming they were published for business, rather than journalistic, purposes.

There is still opposition to the big takeover of CNN’s parent by Paramount Skydance. It comes from some state attorneys general, from anti-monopoly lawmakers like the Massachusetts senator Elizabeth Warren and others. Regulatory hurdles, both in the US and Europe, still could trip things up.

If Ted Turner can exert any influence from the non-earthly realm, I’m sure he’ll be pulling for divine intervention that would keep his brainchild from harm.

In the meantime, those of us still in this troubled temporal world should be hoping that CNN retains editorial independence and serves the journalistic purpose that its visionary founder had in mind from the start.

• Margaret Sullivan is a Guardian US columnist writing on media, politics and culture