Obviously not OP and not in this position, but I have worked with people who left surgical training positions and their reasons were health and a realisation that they would miss every family milestone, never get a real break and have every part of their life revolve around their job with the money and god-like power not compensating for that.
Obviously that’s one side of the equation, I don’t have any surgeon friends I know well enough to give the opposing view.
OP said "did" implying finished. It's a six year residency minimum, though the first year is general surgery. It's not often people do the whole damn thing, then decide to bail. Usually it's after 2 or 3 years
Though some people are less burdened by golden handcuffs and sunk-cost fallacy
Plus, I've never met a happy (or sane) neurosurgeon
I'm in no way even close to being in the medical field, but I could see it as an unreconcilable dichotomy between the hippocratic oath and the fact you're going to be causing damage no matter what.
Sure, the hemmhorage needs to be fixed, so you're preventing further damage, but every cut may cause unknown ramifications. Anyway, I'm postulating a neurosurgeon would be aware of this, and have to carry that around with them.
Medicine as a career offers immense personal fulfillment, variety, human interaction, and prestige at the expense of dealing with difficult outcomes and ranges of personal sacrifice -- neurosurgery as a specialty just takes all of these to their extremes.
I value the former and find ways to discount the latter. So I am very happy. Though sane or not would be up to others.
Obviously that’s one side of the equation, I don’t have any surgeon friends I know well enough to give the opposing view.