Before calling somebody a lousy historian, you should try reading some history yourself.
Nicaea wasn’t a conclave. It was a council. A conclave is convened to select a pope. A council is convened to handle a problem. Nicaea was convened by Pope Silvester and Constantine to address the Arian controversy. Arias was teaching that Jesus was a creature. This created a controversy that was causing problems in the eastern empire. Constantine wanted the Church to settle the controversy. He made the opening address to the council and then took no further part.
The council determined that Jesus was ‘.. of one substance with the Father’.
For more information on the council, here is a link: