The early phases of Turkish conquest of Western Anatolia--during the beylik period, mostly--involved a great deal of destruction, mass murder and enslavement that drove the Greeks of many of the river valleys/interior highlands to coastal cities, the islands or Peninsular Greece. I know that Michael VIII and Andronikos II (and other emperors, IIRC) evacuated the Greek populations of the Anatolian frontier to more 'defensible' regions in Europe as well, so the Islamification isn't so much voluntary conversion as it is depopulation and 'convert-or-die' tactics from the ghazis. The Ottomans eased up on the forced conversions, hence why Peninsular Greece remained Orthodox while their Anatolian brethren didn't.
Also, I've been told (but not given a source) that many of the Greeks in Western Anatolia migrated/returned their during Ottoman rule, but that's basically hearsay.
Another thing worth noting from this Turkification of Anatolia documentary:
It said that a lot of churches and Christian organizational structures in the Anatolian interior were destroyed in the centuries that the Anatolian interior was under Muslim rule. So, devout Christians found it harder to find churches and church leadership to organize themselves and to rally behind. This might have very well made mass conversions to Islam in the Anatolian interior easier relative to mass conversions to Islam in Greece, where churches and Christian organizational structures (parishes, dioceses, et cetera) might have been less damaged as a result of centuries of Muslim rule.
@History Learner Did you ever actually watch the entire documentary above? Because it not, then you should. It's only 20 minutes and it's very interesting. I'm speaking as someone who myself personally previously watched all of it.