The Fed began buying government-backed debt in huge quantities at the outset of the pandemic to calm bond markets.
Once conditions settled, it bought bonds at a pace of $120 billion, and continued making purchases even as it became clear that the economy was healing more swiftly than many had anticipated and inflation was high.
Fed made its final purchases in March. Because officials preferred to stop buying bonds before lifting rates, that delayed the whole tightening process.
Jeanna Smialek NYT 4 May 2022