Christians weren't in suspended animation waiting for religious leaders to develop creeds and such.
No, the bishops were out zealously teaching and evangelizing. But the Faith was still developing 300 years later - look at the differences between the three major Creeds - the Apostles', the Nicene (and the further Nicene-Constantinople), and the Athenasian. The early Church didn't teach explicit Trinity - that came centuries after. And many major Fathers of the Church were lost when they could not accept Church definitions (usually in response to major heresies) such as Origen.
Abide in me, and I in you. As the branch cannot bear fruit of itself, except it abide in the vine; no more can ye, except ye abide in me. I am the vine, ye [are] the branches: He that abideth in me, and I in him, the same bringeth forth much fruit: for without me ye can do nothing. - John 15:4-5
The greatest problem that the early Church (and come to think of it, the current Church) had is just what that abiding consists of and getting people to actually abide.