The message we would like to get across is that this is really the work of the Holy Spirit to bring the Gospel of Jesus Christ to the world through the Virgin Mary. People have gotten so far away from God, and this is a very urgent call to turn back to Him. I guess to sum up what She is trying to say is that people need to have peace within themselves, and that this can come through prayer, conversion and of course communion. I'm not trying to transform anyone to Catholicism, nor is that the purpose of the message of Medjugorje. It is a personal commitment for everyone in the world.
Nobody knows why it was built so large.
As I said, the Blessed Virgin is very happy with the people of the church here. They used to last 20-30 minutes. After the apparitions, Mass is held and then the kids stay in the church for a while longer, staying about three hours daily. They also spend up to four hours a day in prayer and fast three times a week. If you've never tried fasting, you should.