Complex sentence: Her uncle Manuel Komnenos died in 1180, and Bohemond espected that alliance with Byzance was not interresting and divorce from Theodora to marry Sibylle de Burzey.
Split into simpler sentences: Her uncle Manuel Komnenos died in 1180. Bohemond believed that the alliance with Byzance would not be beneficial and divorced Theodora to marry Sibylle de Burzey.