> most dollars are created not by the government, or even the Federal Reserve, but by private banks, via a mechanism which I will not pretend to fully understand

Fractional reserve banking. Basically, bankers start getting very anxious when they see the masses of people depositing mountains of cash into them. They look at the cash hoard they have suddenly amassed and think, we can't just leave this pile of cash here doing nothing, we have to efficiently allocate all of this capital. So they lend it out to people who need cash, charge interest and pay account holders their yields.

Deposit $100. Bank loans out $90, and $10 sits in its reserves. Your account still says $100, even though the bank is now leveraged against loans to third parties. Guy who took the $90 loan pays some bills, and that $90 ends up deposited right back into the same bank. So it keeps $9 and loans out $81. There is now $100 + $90 + $81 in circulation, but only that $100 is real money, the rest are all made up. They only become real when loans are repaid. So, the $81 gets spent, deposited back into the bank, and so on, and so forth, expanding the money supply like a fractal until the amounts become too infinitesimal to track. Thus $1,000 easily becomes $100,000 literally overnight. Government could run its presses 24/7 and it would not be able to outcompete the banks when it comes to inflating the money supply.

Banks are the financial call stacks of society. Better hope there aren't any exceptions (defaults), or the whole thing unwinds and comes crashing down.

It's like a society wide financial version of ISP oversubscription. The assumption is nobody is going to stress test the system by saturating the link 24/7. Everything breaks the second the invariants are violated. Banks similarly assume that not everybody will need all of their dollars immediately, which lets them "efficiently allocate" all of those dollars. Entire government systems exist just to bail out the banks where this assumption fails to be load bearing.