They took Jerusalem, securing it for Christendom and famously killing a lot of people in the Alaska Mosque. Now, the crusaders succeeded in part because the Turkish Muslims, who were Sunnis, did not step up to help the Egyptians, who were Shia. But that kind of complicated, intra-Islamic rivalry gets in the way of the awesome narrative. The Christians just saw it as a miracle. So by 1100 CE, European nobles held both Antioch and Jerusalem as Latin Christian kingdoms. I say Latin to make the point that there were lots of Christians living in these cities before the crusaders arrived. They just weren't Catholic, they were Orthodox, a point that will become relevant shortly.