Complex sentence: On the other hand, Posidonius, like Eunus, was from Syrian Apamea, and the details about Eunus'worship of Atargatis probably arise from his personal knowledge of the goddess's mendicant priests.
Split into simpler sentences: On the other hand, Posidonius, like Eunus, was from Syrian Apamea. Details about Eunus'worship of Atargatis are likely based in his personal knowledge of the goddess's mendicant priests.