1. The division was fixed so quickly(in comparison to today) because the Church of God was in it's infancy and each Christian Church of the time respected and Acknowledged the Apostles as the true and faithful ministers of the Lord. Today we do not have such a people, each group does not acknowledge one group of people in the same way as they did the Apostles. The Lord does indeed still Choose people to go and fix the division within the Church(world wide/spiritual Church) but none of the Denominations(Catholics, Orthodox, Lutheran, Baptist, Etc) accept these people as sent by God. The most that one can hope to achieve is to bring other individuals from each denomination to the truth.
2. Because each is called to God but they often times only remain with the doctrine they have already received without looking further for more enlightenment by God's word(being guided by his Spirit). That is how the Division persists.
3. God does not teach division and confusion. These things come only from the devil and the sinful nature of man.