Only working at my current job until I find something in my field, how do I explain?

Hi all, I originally graduated from college with a degree in Business Administration back in May and I got a job as a bank teller, hoping to work in banking. The people there were horrible to me and I quit after 6 months, going back to my old job that I worked at during breaks in college. The manager there knows that I’m only there until I find something to get my career back up and running, but how do I explain the situation to potential employers?