"Since this is so "clear", it is interesting that it took the church 300 years to dogmatically declare this as orthodox Christian doctrine."
To which "church" are you referring? The RCC, in its catechism, states that Christians and Muslims worship the same God.
I'm referring to the generally accepted (by Christians, of course) councils of the 4th century. From the time of the apostles until the time of Nicea, there were numerous competing "christologies". The "orthodox" formulations of the divinity of Jesus and of the trinity did not come into their final form until the end of the 4th century. At which time all earlier christologies were retroactively labelled "heresies".