What does it concretely mean to "consider the background and reasons of a troubling behavior"?

A troubling behavior usually has the child's own "purpose" or "reason." Common ones are: (1) a request (want, or want to do), (2) escape (dislike, or want to get away), (3) attention (look at me), and (4) sensory (feels good, calming). Observing what happened before the behavior (the trigger) and what happened after (the result) reveals the reason. Once you know the reason, you can teach them to meet that purpose in a desirable way. Rather than just stopping the behavior itself, understanding the "why" and replacing it is the fundamental support.