Allah said be and it began to be. So unless it had reached the perfection, the perfect religion could not be revealed. Stage by stage, man was progressing towards civilization, towards a social realization which developed further into many systems and it was progressing as a man but divided up into so many clans and factions and original tribes and people and there was communication had not yet developed so far as to make the social animal of man into one entity as such.
So at that stage how could a universal religion be revealed? It would be a very naive God to reveal a universal religion to man while the man had no concept of universe either. It was just a religion, regional and parochial thinking and parochial development of various human activities in sociology, in politics and things. So the time was not right for that perfect religion to be revealed to man at that time.
