He was never a Pontiff of the Church, but was the first Pontiff of the Roman State to make Christianity the official state church. His support for the counsel coming together had to do with one of his secular responsibilities, promoting peace within his domains. Forcing a consensus by the ecclesiastical community in a range of areas where there was disagreement & disunity put the ball in their court& yeah, he put his thumb heavy on the scale to push them to make sure their determinations were going to acceptable to him, cuz he was going to have to live with the results.
constantine never made Christianity the state religion either *sigh* does anyone know history?!?