The Muslims Bosnians were Bogomils (Gnostic dualists) until the arrival of the Turks. They didn't want to accept either Orthodoxy or Rome. So they found Islam liberating? Don't quite get it except for the fact they wouldn't have to pay the jizya that all dhimmis were subject to.
Bosnia was Serb state, ortodox Christianity, king Tvrtko took name King of Bosnia and Serbia. There was Bogumil movement, but not as large as belived. Also there was Pataren movement in Serbia.