According to churches that consider ecumenical council decisions final, trinitarianism was infallibly defined at the First Ecumenical Council (the Council of Nicaea) in 325 A.D.
^^ Davis, SJ, Leo Donald (1990). The First Seven Ecumenical Councils (325-787): Their History and Theology (Theology and Life Series 21). Collegeville, MN: Michael Glazier/Liturgical Press. p. 68. ISBN 978-0-8146-5616-7.
Church and state in Europe suppressed nontrinitarian belief as heresy from the 4th to 18th century.
The early Christians had no idea what you guys are ranting on about. They worshiped God alone, they followed Jesus (pbuh). The trinity is a later invention and all the other doctrines you are trying to propagate that justify to you the worship of a man.
The following narration recorded in the Qur'anic exegesis of Ibn Kathir is graded as authentic by orthodox Sunni scholars and provides a plausible explanation for the Qur'anic verse related to the substitution of Jesus:
Ibn Abbas said, "Just before Allah raised Jesus to the Heavens, Jesus went to his disciples, who were twelve inside the house. When he arrived, his hair was dripping with water (as if he had just had a bath) and he said, 'There are those among you who will disbelieve in me twelve times after you had believed in me.' He then asked, 'Who among you will volunteer for his appearance to be transformed into mine, and be killed in my place. Whoever volunteers for that, he will be with me (in Paradise).' One of the youngest ones among them volunteered, but Jesus asked him to sit down. Jesus asked again for a volunteer, and the same young man volunteered and Jesus asked him to sit down again. Then the young man volunteered a third time and Jesus said, 'You will be that man,' and the resemblance of Jesus was cast over that man
while Jesus ascended to Heaven from a hole in the roof of the house. When the Jews came looking for Jesus, they found that young man and crucified him. Some of Jesus' followers disbelieved in him twelve times after they had believed in him.
They then divided into three groups. One group, the Jacobites, said, 'Allah remained with us as long as He willed and then ascended to Heaven.' Another group, the Nestorians, said, 'The son of Allah was with us as long as he willed and Allah took him to Heaven.' Another group, the Muslims, said, 'The servant and Messenger of Allah remained with us as long as Allah willed, and Allah then took him to Him.' The two disbelieving groups cooperated against the Muslim group and they killed them. Ever since that happened, Islam was then veiled until Allah sent Muhammad."
—
Al-Nasa'i, Al-Kubra, 6:489