When a bank goes bankrupt that effects equity and the owners of the banks. But the borrowers are still obligated to repay their loans. And it is those repayments what enable fiat currency holders to get resources (labour, services and products) from the borrowers. In that way, debt in which they invested by receiving fiat currencies, is paid to them.
Unsecured creditors are not the first in line to have their funds recovered when banks fail. Savers often lose out. This is why the FSCS exists. Stop pretending that it's a magical world of make believe where bank balances are somehow left intact when the company that printed them from thin air becomes insolvent.