The person leaving quietly may have spent months asking in ways nobody recognized as serious.

A resignation that looks sudden is usually the visible end of a long private process. The requests came earlier, phrased mildly, delivered as hints because the stronger version felt risky, and each was heard as a grumble rather than a warning. By the time it looks dramatic, the deciding is already finished.

If someone has raised something twice, treat the second time as serious even when it was said lightly. Ask directly whether it is a problem or a preference. And if you are the one hinting, try the plain version once before concluding that nobody is listening.