Lol George Bailey was not a bank manager- he ran a family business, a building and loan, a community funded way for working class people to get access to credit and loans to buy homes, gaining access to the middle class.

The bad guy in the film, potter, is a banker. He tries to collapse the building and loan by promoting a Run on it. If he can scare the citizens enough they’ll pull deposits from the building and loan, making it insolvent, and potter will be the only source of credit in town and be able to gouge the citizens. He’s a monopolist.