Why has the Fed been so hesitant to meaningfully sell Mortgage backed securities that are no longer underwater when rent is arguably the biggest driver of inflation right now? Informed/quantitative replies only.

For context, MBS have been stuck on the balance sheet for the last 16 years and account for about $2.35 trillion of the balance, sheet, two thirds of the size of the U.K. stock market. I understand that the Fed has a mandate to make money, but my searc…