جَاءَ رَجُلٌ، ثُمَّ تَكَلَّمَ الرَّجُلُ.
A man came, and then that man spoke.
The initial indefinite introduces a participant, and the definite reference points back to him: anaphoric definiteness (ʿahd dhikrī). Calling every definite article magnification would obscure the link between the two clauses.
Definiteness may serve other effects in suitable settings, but editing should begin with the clearest local evidence. A speculative secondary effect must not replace an obvious identification function.