Laziness mostly. It takes at least a decade of sustained exhausting mental and physical work to become a doctor, becoming a thief is mostly opportunity.

Some combination of desperation and sociopathy.

I might suppose that it's usually more the former than the latter, but there's degrees to each characteristic.

They perceive that they need things, and they don't necessarily care who they harm to get the things that satisfy this need.

(When we dress it up all nice and back it with corporate layers and an army of lawyers, sometimes we get CEOs.)