So, why Syria and not Bulgaria? Is there an Orthodox point of view about this?
I don’t think there is a ‘church approved’ explanation for anything, but I have opinions.
It requires an examination of history, and unfortunately none of us were there, so everything is open to speculation.
I am pretty sure there were still pagans around in the eastern empire at the time of the Arab conquest. They were forcibly converted. So the Christians and Jews observed foreigners (Arabs from the desert) and former pagans catapulted to the privileged places in society.
There is about a 700 year difference (or more) between the Arab explosion into the Levant (and north Africa) and the Turkish expansion into Europe. That’s about twice as long.
For most of that time, in both cases, the Muslims did not do much forcing of conversions of Christians and Jews, in fact the authorities often discouraged it. The reason was that there were punitive taxes and discrimination against “people of the Book”. If the people converted, they did not pay these taxes (and I think there was something about a ban on the forced conscription of Muslims, but I am having a hard time remembering what I read on these points).
Now this was not a free society. Christianity could not compete in the marketplace of ideas because conversions could only go one way: into Islam, not from Islam.
One piece of current conventional wisdom states that a parish needs to add 6% of it’s membership every year in order to keep an even (or consistant) population, just treading water. This accounts for death and people moving out. To expand the parish should try to beat that number. I don’t know how accurate that is but I remember reading that at one time.
Another thing I remember reading (I have no stats for this) was that Christianity in Egypt, Palestine, Anatolia and Syria was actually still the majority religion (declining, but …) until the time of the crusades, after which there was a heightened amount of retribution on the local Christians, and the numbers started to decline more rapidly. We are seeing this kind of accelerated decline among Christians in Iraq again these days.
In this kind of situation those who can leave often do, and if for any reason the birthrate falters or the number of people converting out of the community rises there will be a negative annual rate of growth. Repeating this 600 or 900 times in a row and one can see how this can become a big problem.
It is noted that north African church completely disappeared. What is often missed by us is that the Mozarabic (native) population in Spain was once on the same trajectory. Probably most of the ‘Moors’ who were expelled at the fall of Granada were actually Mozarab Spanish families who had converted at some point in the 700 year occupation (naturally there were Arabs and Berbers too, but it is known that the native Spanish had assimilated to the point that most spoke a form of Arabic and that is usually the first big step in the process before large numbers fall away).