This source claims the Bishops/Church Fathers were forced to sign the decree at Nicea.
Encyclopedia Britannica 1968
"The Council of Nicaea met on May 20, 325. Constantine himself presiding, actively guiding the discussion, and personally proposed the crucial formula expressing the relation of Christ to God in the creed issued by the council 'of one substance with the father.' Over-awed by the emperor, the bishops, with two exceptions only, signed the creed, many of them against their inclination. Constantine regarded the decision of Nicaea as divinely inspired. As long as he lived no one dared openly to challenge the creed of Nicaea."
Encyclopedia Britannica 1968
"The Council of Nicaea met on May 20, 325. Constantine himself presiding, actively guiding the discussion, and personally proposed the crucial formula expressing the relation of Christ to God in the creed issued by the council 'of one substance with the father.' Over-awed by the emperor, the bishops, with two exceptions only, signed the creed, many of them against their inclination. Constantine regarded the decision of Nicaea as divinely inspired. As long as he lived no one dared openly to challenge the creed of Nicaea."