What a central bank says, as much as what it does, affects those expectations. Even more important are expectations of future inflation. When people expect prices to rise rapidly, they bring forward purchases, put up their own prices, demand higher wages and so on. That helps to create the very inflation they expect.
A second example of the public sector playing a stabilising role was provided during the 2008–09 financial crisis, when governments issued bank funding guarantees. During that period, risk aversion soared, capital markets shut down, and even the well-rated financial institutions found that they could not raise funding and provide critical financial intermediation services to the broader economy.