Complex sentence: Knyaz Boris realized that the Christianization of his subjects would result in the spread of Byzantine influence, as the liturgy was carried out in the Greek language, and the newly established Bulgarian Church was subordinate to the Church of Constantinople.
Split into simpler sentences: Knyaz Boris realized that the Christianization of his subjects would result in the spread of Byzantine influence. The liturgy was performed in the Greek language, and the newly established Bulgarian Church was subordinate to the Church of Constantinople.