This is a "developer acts individually over being in or leading a team" type question, but at a much higher level.
We're a small fully-remote business with a successful product solving several overlapping complex industry problems, but seen as unreliable and struggling to grow. It's hard to ignore much of this is caused by the CTO we'll call Carl.
Carl the CTO is a talented and prolific super-coder with deep technical knowledge who built the entire platform himself - and an excellent Individual Contributor - but has trouble with the bigger picture and teamwork, due to these main problems:
a) only Carl really knows how the platform works, what features it has, how to use it, etc.
b) Carl is easily distracted, often by customers or salespeople who directly contact him
c) Carl has a do-ocracy approach and can act unilaterally and unpredictably
d) Carl often over-commits, or fails to commit, forgetting or trivializing agreed work
Think of Brent from the Phoenix Project, but he seems to LIKE being Brent.
Carl is simultaneously the goose that lays the golden eggs and the kudzu choking everything off.
The CEO keeps a running list of "urgent Carl jobs" which Carl commits to with the breezy confidence of someone who knows they can hand-wave their way through anything. Sometimes he does them. Sometimes he'll get distracted by something trivial for the rest of the day, repeat tomorrow. Sometimes he'll describe at length what he is going to do... and then stall for weeks.
We find a customer Slacks him with a feature request, bug, &c. Carl goes "what a good idea", and does it on the side without telling any of us, or any other customer, who needs and would pay for it. Or worse, he lets them down due to being over-committed / distracted by OTHER hidden work, us only finding out when the customer escalates.
People quickly learn "the only way to get something done is to get in front of Carl" - start a video call with him, where he cannot ignore the problem and fixes it on-screen, sometimes in seconds. Frustrating for everyone - especially if it's a simple problem that's blocked customers for months.
We are often surprised by our own product; critical projects are so behind we largely give up on them, often giving up on which fire to fight first; we're getting into trouble with the industry regulator; and so on. Some customers love him, he's their concierge AND a rock star. Others... do not.
The CEO is well aware of this, and seems to overlook Carl's behaviour, despite the problems it causes. "Without Carl, there'd BE no business." We have tried:
Change process / shield: prevent customers or salespeople from distracting him, change our use of Slack, use JIRA to track work, etc. No impact: they email him directly, and set up calls we find out about afterwards. We have found customers adding him to THEIR Slack, project calls, etc. as if he's their contractor, which he goes along with.
Delegation: hire developers, product people, support staff, etc. to help and learn from him. Mixed: he tries, but sees them as a distraction instead of tools to increase his reach. He struggles to find them work, preferring to do it directly, and likes it when they are out sick / on vacation.
Learn: write down how things work, so he's not the bottleneck. No impact: The platform is complex, he wrote it himself, and much of it lives in his laptop / his brain. Asking for documentation turned into a help system for each page in the platform, but apart from a couple of test pages, it's empty. Note that somehow he has spare time to write a custom help system, but no time to put anything into it.
Split into workstreams: using the above. No impact: everything, from the help to the login system to the support email are, somehow, an in-house system only Carl understands. We are paying expensive contractors to do nothing as they wait for Carl to spec, review (or re-write) their work, which he has to wire up behind the scenes. We cannot even create a test server after years of trying; Carl's laptop is used for QA.
Understand Intent: borrow from Situation, Behavior, Impact - learn why he acts this way, what drives him, his goals, etc. Mixed: He loves coding and solving technical challenges, and describes himself as "multitasking" or "being customer focused". Conversations then switch into fixing the problem in front of him - usually something he is way too talented for, but he clearly likes doing, especially when only he knows what to do and - he thinks - justifies working long hours to help them.
Asking Nicely: like rolling dice.
What else can we try to change this behavior?
EDIT: I am a non-C-level staff with no equity or stake beyond an employee who wants them, and where I work, to grow and succeed. They are nice people to work with and have good humor, especially Carl. Been trying to learn the platform as much as I can, but it's trial and error and I've often looked an idiot with customers who know the platform better than we do.