Nah, I don't know specific examples that satisfy the OP's original question, but writing for entertainment (and showrunning as a management-level tier of that track) is just a career transition like any other.
People who've had one professional career and been grinding on their writing on the side absolutely make the leap and move their way up. Often, their break comes from writing from their expertise. If you dig through shows about medicine, law, policing, etc etc, you'll often find several writers who were worked in those fields.
Not every writer was a barista until they made their break. Some of them were indeed lawyers and engineers.
This sounds like you are talking about people transitioning to being a writer, not a show runner.
That's like someone saying "has anyone transitioned to running cartoon network?" and someone else saying "people have transitioned to being an animator, which is almost the same thing".
No, there are many showrunners. It’s essentially just a management-like writing position for any of the thousands of scripted programs that produced each year.
It’s an achievement to be proud of, just like being a partner at a law firm or an mid-high position at a high-profile FAANG, but it’s not as rarified as you seem to think.
They’re not in charge of the project any more than any other project/product manager.
Somebody else is still making final go and stop decisions on their projects, setting their budget, demanding stupid details, etc. They’re just in charge of wrangling some of the creative and production processes and get to take credit for the overall creative vision of the project (or blame their execs/peers/staff if they’re unhappy with it). Literally the same as in any other industry.
I don’t know why I keep replying, but any reasonably social 40+ adult who had lived in SoCal personally knows showrunners as well as people in most other roles in the industry. Some have even held some of those roles! This isn’t some made up basement-dwelled bs that I’m sharing with you; this is actual ground knowledge.
I don't think you understand what a showrunner is.
The showrunner is in charge of the stop-and-go decisions, the details, spending the budget allocated by the studio. They hire the key crewmembers (DOP, lead writer if not the showrunner, casting director, etc. who then build out the cast and crew. They are as in charge of production as they choose to be: some showrunners micromanage, while others let their crew have a relatively free hand to do their jobs.
Of course the studio (usually) has final approval; they're paying for the show. But that doesn't mean the showrunner isn't the boss. It just means that...like every CEO...they still answer to the person with the piggy bank.
Also, showrunners aren't as common as you seem to think they are. You might be mixing up showrunners with producers? Producers are as common as weeds. Frequently, writers and cast members are given producing responsibilities and credits for an episode or two, as are many investors, and generally anyone who handles a task that is in any way related to production and has the leverage to demand some sort of credit.
You might be confusing a 'runner' on a show, which is an entry level production position with 'show runner' which would be the person in charge of the entire show.
Very few people don't operate under constraints. Even an executive producer (= showrunner) who owns their own production company needs to sell their projects to clients though there are presumably more options these days and people supplying money do expect some say in the final product most of the time.
But that's true of Oscar winning directors and senior partners at architectural firms. It's even true of the studio boss if he's had a string of flops.
People who've had one professional career and been grinding on their writing on the side absolutely make the leap and move their way up. Often, their break comes from writing from their expertise. If you dig through shows about medicine, law, policing, etc etc, you'll often find several writers who were worked in those fields.
Not every writer was a barista until they made their break. Some of them were indeed lawyers and engineers.