Fractional Reserve it was called. And it's now an Empty Reserve.
Besides the pump from 2021 can be justified from the monetary mass injected from FED and other Central Banks https://fred.stlouisfed.org/series/CURRCIR
Thanks for sharing such great (and well explained contents)!
When your car's reserve is empty, you aren't going anywhere fast :)
And yes, the monetary mass caused the pump, but they had even more to play with, as they didn't have to store any of it for a just in case scenario.