Did this happen to the writer? No, not always.

Your question should be... What did the writer have to know, feel, notice, imagine, or understand in order to make this believable?

A writer's imaginative range is partly determined by their habitable inner world.

A person can experience something intensely and produce a passive writing about it because they lack accurate articulation, language for it or just don't want to pen it down. Another person can experience very little to nothing of similar instance personally and produce extraordinary writing because they can inhabit another consciousness with perfect precision and flawless diction.

You don't have to have been a murderēr to write a murdérer. You don't have to have to have lived for 80 years to write an 80 year old protagonist. You don't have to have experienced war to write about a soldier getting married in the center of a bloody field. But you need some level capacity and information to construct the consciousness of that person and to make their motives, challenges, contradictions, behaviour, and worldview intelligible from the inside.

Experience can ignite a creative spark. Imagination can gives you another route as well, people's stories and intentions can provide the material.

But you can only write believably from a territory you let your mind enter, or where your mind can enter.

An ideal writer, creates from the things they've lived, and how well they've fed their imaginative mind.

You pour out from what you can understand, observe, simulate, and inhabit. You can't create ex nihilo.