When an unanticipated increase in real interest rates occurs, the winners are the banks.
This is because some contracts are pre-fixed, however, other contracts are based on the real interest rate. This rate has a predictability anchored in the expectation of economic agents regarding the position of the Federal Reserve.
If an event occurs and the Fed increases interest rates higher than expected, the financial agents that have interest-linked contracts pay according to the rate, ie, the banks receive this difference between the expected interest rate and the effective interest rate .