Would there still be crusades? After all, the crusades started after the Byzantine emperor asked for help. The situation in Syria/Palestine would develop differently if the Byzantines had won at Manzikert. Of course, the answer depends on what would happen after Manzikert. Would the Byzantine empire expand its area? Would perhaps the Fatimid Caliphate be strengthened? If the Seljuq sultanate was weakened, maybe the Fatimid would have taken control of Syria, with Palestine?