I think that's too large and nuanced a concept for one word or phrase to encompass, but there may be appropriate phrases for parts of it that you may find useful. (Besides the obvious expletive powered ones!)
First off, doing more than you needed to is called overachieving. One specific act of overachievement can be said to be going above and beyond.
Being tasked with more than you can actually deliver is to be overstretched, while working right up until you're exhausted is to be stretched thin.
When something is unique, and unlikely to be repeated, it's referred to as a one-off.
Doing something detrimental to yourself, intentionally or otherwise is shooting yourself in the foot.
When you set out to do one thing, but another detrimental thing happens instead, you can say that the venture backfired
Being forced to choose between two equally bad outcomes is to be damned if you do, and damned is you don't. The actually choice it's self is a dilemma.
When an employer makes unreasonable demands, you can say that they're turning the screws, illustrating the act by referring to an old torture device: the thumbscrew. The interesting parallel here is that the thumbscrews were turned incrementally, slowly crushing the victim's fingers.
To take on something that you can't really deliver is to bite off more than you can chew.
Working overtime is often called crunching or cramming, both bringing to mind the act of smashing right up into a deadline.
To begin a heavy effort activity in earnest can be indicated by rolling up your sleeves.
Committing to the new schedule is a foolish act. It's an act of folly. It is overoptimistic, unsustainable and doomed.
There's also an element of learning the wrong lesson here, which is where someone makes the wrong conclusions from observing an experience.
Making bad management decisions is just mismanagement.
So in conversation we could cherry pick and try something like:
Rolling up their sleeves to crunch for a week and double output backfired for a groups of employees whose bosses then turned the screws and foolishly expected the same going forward.
One surprisingly common act of mismanagement is dooming your workforce to meeting their stretched thin overachieving one-off performance the rest of the time. Employees that shoot themselves in the foot this way are then incentivized to underperform and lower expectations instead, benefiting no one.