I obviously don’t condone his methods but I do have to respect his creative drive.
As an exercise:
Why does your character (hero or villain) steal? Is it to feed himself and his family like Jean Valjean in Les Miserables? Or to get revenge against a former employer like Woody Harrelson’s character did in Money Train? Or maybe it’s to protect a family member’s reputation like in How To Steal A Million…
Even if your character doesn’t steal something in your story, imagine they do. By deciding what it would take to drive them to steal, you can learn a lot about them. And no one said they have to steal money or priceless works of art. Maybe they just steal the girl 😉