The ECB initially responded to the disruptions in the money markets by providing overnight liquidity and additional liquidity with a maturity of one week in its main refinancing operations. However, tensions persisted with regard to longer maturities. The ECB responded with longer-term refinancing operations.
My starting point would be that the Federal Open Market Committee did what it thought was appropriate ex ante to return the economy to full employment and stable prices, taking Treasury decisions concerning debt management as exogenous.