People reveal a lot about themselves in the answers to simple questions. In your case, perhaps some things that people might see as a negative. For example, if your sick parent worsens, will you need accommodations such as time off? If they get better, will you no longer need the money and go back to research? Are you willing to take pretty much anything as long as it pays well? (Nobody wants to be your "pretty much anything".)
Wanting to make more money is a perfectly fine reason for wanting to change jobs. And research is well known to be a lower paying career. So work on a few sentences like this:
I have enjoyed teaching and research, but there are some things it doesn't offer me. I would like to do more X, and to have a career path that can be rewarding both financially and in job satisfaction.
I have no idea what X is, something you can do at the bank that you can't where you are now, but it might be meeting customers or helping businesses thrive or knowing you're contributing to a larger project or whatever. You need to know that before the interview, because you'll look foolish if you say you want something they don't offer, or won't offer for a decade or more until you rise up in the company.
It's always a good idea to answer about what you want more than what you want to leave behind. Not making enough to actually live on is nobody's business. Wanting to be well rewarded for your skills? That's something you can learn to say with a big smile.