A significant reduction in overhead would free significant funds into the hands of the consumers, who would employ them to improve their lives, generating economic growth and demand in other economic areas that would pick up the slack. Granted, it's not comfortable for the workers made redundant, hence the tendency to band together as a special interest group and put political pressure to keep things inefficient (that's all assuming single payer is indeed an efficiency improvement, an entirely separate discussion).
If the facts on the ground were that it was actually possible to get single payer passed, I think those questions would have been easily answerable. It just wasn't tactically necessary to answer them in the context of what was achievable because of one horrendous (sorry Lieberman, but you really blew it) person.
The statement was clearly entirely political, of course.
"What will happen to them" doesn't have to mean preserving a broken system, it just has to mean caring humanely for those affected.
Also according to that article, former coal miners are more open to retraining where other industries have jobs readily available and/or where coal has no credible chance of comeback in that area.
None of that contradicts my suggestion as applied to the health insurance industry, which isn't really part of any cultural identity, and which would clearly not be about to rebound quickly in a single-payer world.
Retraining could even be pretty quick if they retrained to other forms of insurance, especially life insurance (which still cares about individual health) but there are many other kinds too.
I mean, sure, it's easy to setup negative incentives if you setup a welfare system and you aren't paying attention, but that's really a different sort of issue... and one that can be solved by looking at those negative incentives. (the earned income tax credit is a good place to start if you want to look at real-world attempts to amelerate the negative incentives that come with "you lose all benefits if you earn more than X dollars" style need-based plans. I'm just bringing it up because it's a real-world attempt to solve that problem and because there is real-world research on it.)
An imaginary way to deal with those negative incentives is Milton Friedman's "negative income tax" or even the 'basic income' people are on about.
But point being, the negative incentives are a thing that you have to watch for with welfare programs... but they don't negate the good done by, you know, allowing poor children to access medical care, food and education.
The discussion here was between welfare and bullshit jobs, not welfare or starving.
The pointless job sucks out many hours of productive hobbies and caretaking, space to think, innovate and organise.
This might be the desired effect - one of the means to control the population.
I tend to be more optimistic and think that the problems arise by our current model of unemployment rather than the idleness by itself, but I can't pretend I know the answer.