Nor would I argue that trinitarianism was not a doctrine of the early church. Therefore, it WAS a doctrine of the early church and deserves our deepest attention.
As this article points out, premillennialism also was a doctrine of the early church.
While the Trinity was never explicity stated in the Scripture, although MT 28 clearly implys it, it would be the development of the Doctrine of the Most Holy Trinity in the Church Fathers which was finally explicitly taught at the Council of Nicea and the later Councils (Constantinopile 381 AD, Ephesus 431 AD, and Chalcedon 451 AD) in terms of the relationshop among the Father, Son and Holy Spirit.
The pre-millinial view, while taught in various forms by some of the Fathers, was never universally taught. Also, it seems to find very little notice in the Eastern Church Fathers. Remember, there were two Theological Traditions, that complemented each other, the Latin-West and the Greek-East. Both traditions came together at the 4 Councils I cited above, but the issue of pre-millinialism by the time of St. Augustine (360-430 AD) had no support, and even though a few Fathers had a pre-millinial view, the Universal Church never embraced it at the 4 Great Universal Councils.
Regards