Below are Christian of various middle east in percentage of overall population according to wikipedia and CIA factbook
Syria and Lebanon fell under Muslim after AD 638, while the whole of today's Turkey was only conquered after AD 1453. Before these dates, these were Christian countries. In short, while Christian still exists in Syria and Lebanon today, after almost 1500 years of Muslim rule, its population fell to 0% in Turkey in around 500 years. And this is despite the fact that Turkey is closest in proximity to Christian Europe than any middle east countries.
Ottoman conquest of Christian land
After the fall of Constantinople in 1453 to Ottoman Empire, the children of Eastern Church found themselves isolated and surrounded by a sea of Muslim population, like an abandon child.
Other than Asia minor, the Ottoman Empire conquered large amount of then Christian land, and even besieging Vienna twice. The last attack of Vienna by Muslim Turk occurred in 1683, just 73 years before the birth of Mozart.
Christian under the Ottoman: The tolerant period
Under the emerging Ottoman, Christians were subject to the whims of their Turkish and Kurdish neighbors, who would regularly overtax them, subject them to brigandage and kidnapping, force them to convert to Islam, and otherwise exploit them without interference from central or local authorities. In the Ottoman Empire, in accordance with the Muslim dhimmi system, they, like all other Christians, were accorded certain limited freedoms (such as the right to worship), but were in essence treated as second-class citizens and referred to in Turkish as gavours, a pejorative word meaning "infidel" or "unbeliever.
At this period, state sponsored mass slaughter generally did not occurred.