Did Constantine start the Catholic Church?

One historian comments: "[Dan Brown says] that Emperor Constantine imposed a whole new interpretation on Christianity at the Council of Nicea in 325. That is, he decreed the belief in Jesus' divinity and suppressed all evidence of his humanity. This would mean Christianity won the religious competition in the Roman Empire by an exercise of power rather than by any attraction it exerted. In actual historical fact, the Church had won that competition long before that time, before it had any power, when it was still under sporadic persecution. If a historian were cynical, you would say Constantine chose Christianity because it had already won and he wanted to back a winner."