Both the Balkans and Anatolia became core regions of the Ottoman Empire. Both started as Orthodox Christian populations with a Roman identity, speaking non-Turkish languages. Anatolia overwhelmingly became Muslim and identified with the Turkish language. The Balkans only did in tiny amounts. I know the first was under Ottoman control longer, but it seems this does not explain the difference, as Anatolia converted faster than the Balkans was under Ottoman rule.
So what explains the difference?
Not sure if acceptable, but if you search for 'population exchange' or stuff on the Balkan/Greco-Turkish wars and limit the results you may find some answers to your questions. Essentially the demographic situation we see today is the relatively recent result of a series of wars and population transfers.
https://www.reddit.com/r/AskHistorians/comments/58p3zs/why_was_the_ottoman_empire_unable_to_mass_convert/ https://www.reddit.com/r/AskHistorians/comments/5ysdpo/why_did_anetolia_become_mostly_islamic_under/ https://www.reddit.com/r/AskHistorians/comments/19rwlf/why_did_albania_and_bosnia_become_majority_muslim/
iI wonder if maps like https://i.pinimg.com/originals/92/b8/00/92b800f009593647a2b4bbcf89a06107.jpg could provide somewhat of an indication since it seems at least some of the time Greek/Turk basically functioned as synonyms for Christian / Muslim?
