Game over happens when, fiat money seems to have, on a risk adjusted, liquidity adjusted basis, a better return and better appeal than holding existing real private assets, therefore a process starts where people, businesses and banks try to hoard government paper all at the same time instead of holding private assets. Demand shifts so far towards government paper and away from private assets that the supply of the later assets go in steep decline (eg. businesses close, people are laid off etc.).
Basically fiat's appeal as an asset, its above market return, puts the private asset market in a gridlock.
It's normal for private asset returns to go negative in a crisis. Before paper money existed, losses on assets were a common thing. Your land would suffer from drought, your live stock would get an infection. You didn't stop working and shut everything down because you temporarily expected to get a poor return. You still wanted to eat something at the end of the year.
The existence of an artificial government asset that has difficulty following the private assets rate of return into the negatives, can sometimes block a large part of the private asset market from existing. Business owners choose to stop any investment, wind down their business and sit on cash. The world moves towards everybody holding pieces of paper and nobody producing anything you could buy with these pieces of paper.
Counter intuitively, in order to prevent people from holding too much government paper, you have to print a lot of it very early to make it seem less appealing.
For example, if toilet paper companies had been ahead of the curve and kept the shelves stocked, they probably wouldn't have needed to manufacture so much toilet paper because fewer would have hoarded it if it didn't look scarce. The fact that they didn't produce enough early enough, means they ended up having to produce more overall.