Complex sentence: Technically the Archbishop of Riga was the feudal and ecclesiastical superior first over the Swordbrothers, later the Livonian Order but the Archbishop did not became the dominant political power.
Split into simpler sentences: Technically the Archbishop of Riga was the feudal and ecclesiastical superior, first over the Swordbrothers, later over the Livonian Order. But the Archbishop did not became the dominant political power.