After the 9/11 attacks of 2001, the ECB and the Federal Reserve entered into a swap agreement to make their currencies available to each other

"After the 9/11 attacks of 2001, the ECB and the Federal Reserve entered into a swap agreement to make their currencies available to each other. 

This enabled the Eurosystem to provide dollar liquidity to European banks, thereby preventing liquidity shortages from leading to risks to financial stability. 

Similar schemes have been in place since the credit crisis, which were further expanded during the COVID crisis. 

The Eurosystem has provided access to euro liquidity facilities to several non-euro area central banks through swap and repo lines."

"The significant liquidity injections and unconventional measures taken by the Eurosystem since 2008 resulted in a more than twenty-fold increase in reserves by the end of 2021. As a result of this excess liquidity, the main conditions for a corridor system were no longer met. Moreover, the strict distinction between monetary policy and the provision of liquidity became blurred, leading to the separation principle, as it preceded the
the credit crisis had to be abandoned."

"However, due to the excess liquidity, banks held more reserves than required by the MRR, on which the interest for the deposit facility is remunerated (the DFR). As a result, the Eurosystem's role changed from a marginal lender to a marginal borrower and the key policy rate shifted from the MRO to the DFR. With the lower boundary of the corridor (the DFR) as the main determinant of money market interest rates, this system became a de facto floor system."

"Since the credit crisis, there has been a shift to floor systems at the major central banks in developed economies.
This development can largely be attributed to the growth of central bank balance sheets due to UMP, which resulted in excess liquidity.

"As a result of the liquidity surpluses, unsecured interbank transaction volumes have decreased significantly. Due to the wide availability of reserves, banks no longer need such mutual transactions to manage their liquidity. As a result, an increasing number of money market transactions involve non-bank counterparties."
 
Read this link : https://www.dnb.nl/media/doybyfyq/web_136944_os_nl_monetairy-operations_v3.pdf

according to De Nederlandsche Bank in 'The Eurosystem's monetary instruments in unconventional times'.

In this study, DNB claims that the ECB's new 'floor system' came about by chance as a result of various crises, but as Worst Bank Scenario shows, this is not the case. 

Read Worst Bank Scenario and discover how in the EU (and in the US, among others) via investment banks such as Goldman Sachs and asset managers such as BlackRock (in the Netherlands thanks to ING and Nationale Nederlanden, among others) a new "monetary" (floor) system has been rolled out by central banks and the ECB (with US FED 'in the lead').