As in another thread, this has already been asked before x times. Please search:
https://www.reddit.com/r/AskHistorians/comments/3nkwcf/why_out_of_all_the_regions_in_the_balkans_were/
https://www.reddit.com/r/AskHistorians/comments/19rwlf/why_did_albania_and_bosnia_become_majority_muslim/
https://www.reddit.com/r/AskHistorians/comments/26aivd/during_the_ottoman_rule_on_the_balkans_why_did/
https://www.reddit.com/r/AskHistorians/comments/1orcen/why_did_some_ethnics_which_were_subject_of_the/
https://www.reddit.com/r/AskHistorians/comments/2gsvlt/why_did_some_balkan_nations_convert_to_islam/?ref=search_posts