Complex sentence: For their part, Ottomans regarded Ragusa as a port of major importance, since most of the traffic between Florence and Bursa (an Ottoman port in northwestern Anatolia) was carried out via Ragusa.
Split into simpler sentences: For their part, Ottomans regarded Ragusa as a port of major importance. After all, most of the traffic between Florence and Bursa (an Ottoman port in northwestern Anatolia) was carried out via Ragusa.