One subject can be expressed with different words, examples, and angles, giving the listener renewed receptivity. Variation of expression is not purposeless change: it can clarify the same truth along different routes.
Prophetic preaching, a people’s response, and their outcome may be narrated in several surahs for different purposes. One passage emphasizes monotheism, another the consequence of arrogance, and another the perseverance of the messenger. The core event remains related, but each occurrence foregrounds a different lesson.
Rhetorical benefit: variety prevents monotony and allows a theme to become more firmly and memorably established.