Final answer:
The Federal Reserve's substantial asset purchases under 'QE4' were aimed at stabilizing the financial system during the pandemic, doubling their assets to over $8 trillion by the end of 2021, and are now in the process of tapering.
Step-by-step explanation:
The acquisition of Federal Reserve Bank (Fed) assets in excess of previous holdings was a strategic decision made in response to specific economic conditions. When the Fed, led by Jerome Powell, launched what was referred to as "QE4" in March 2020, this decision was aimed at providing liquidity to the financial system during the economic distress caused by the pandemic. By the end of 2021, the Fed's assets had doubled from $4 trillion to over $8 trillion, revealing the significant scale of asset purchases. The Fed has since started to taper these purchases, with expectations that the pace of tapering will increase through 2022, signaling a careful unwinding of these extraordinary measures.