Founded by mere man? Let us assume that Jesus gave initial revelation via his insight and through his life, with regard to a set of doctrines which are ultimately true. Such doctrines were then taught to the world, from the mouths of those who knew Jesus. The world, in turn, taught generation after generation.
Of course, men argued over who had the most authority to teach in the name of Christ, and this in turn led to different sects arising. When the Roman Empire officially began replacing classical Roman polytheism with Christianity, councils were called to ‘settle’ such arguments. Submission to the will of councils, then, became a hallmark of the authority of the men teaching in the name of Christ. Such authority formed canon. When it was time to philosophize, the Neoplatonist positions were overhauled to suit Judaic theology, and thus in turn influenced the initial doctrines of Jesus, of Paul, and of the traditions of the Apostles.
I would have to say that this extremely simplistic (this is a forum, afterall) view of events, certainly leaves far more room for the founding of Churches by ‘mere men’ then it does for the founding of a Church by Christ. Indeed, there is nothing ‘known’ about Christ which men themselves did not preserve for other men. The first centuries of Christianity were an organic period of growth, based on the initial beliefs about the life and teachings of Jesus, rather than a structure which was, in every respect, set out in stone by Christ in an utterly obvious manner. The room for disagreement is vast.
