Complex sentence: As Venice's relations with the Byzantines were temporarily disrupted by the Fourth Crusade and its aftermath, Genoa was able to improve its position, taking advantage of the opportunity to expand into the Black Sea and Crimea.
Split into simpler sentences: As Venice's relations with the Byzantines were temporarily disrupted by the Fourth Crusade and its aftermath, Genoa was able to improve its position. Genoa took advantage of the opportunity to expand into the Black Sea and Crimea.