حَضَرَ التُّجَّارُ فَفَحَصَ الْمُرَاقِبُ مَوَازِينَهُمْ، ثُمَّ كَتَبَ التَّقْرِيرَ.
The merchants arrived, so the inspector checked their scales, and then wrote the report.
Fa links the inspection closely to the arrival, often marking sequence with immediate consequence. Thumma makes the report a later stage, allowing an interval. Wāw would provide broader coordination without carrying that same inherent ordering force.
No particle alone specifies an entire timeline; context supplies the rest. Differences among conjunctive markers are differences in meaning and discourse structure, not decorative variants.