The New Testament did not drop out of heaven. It was authored and published in the same manner as any other book. 2 Pet 1:21 describes how men were carried along by the Holy Spirit like a boat is carried along by the wind. They were not replaced by God but he managed the process. There is no angel whispering in a cave to one person in the Christian view of inspiration. We have multiple attestations with historical veracity of the public deeds and words of Jesus, his apostles, and their followers. We have overwhelming evidence that the 4 gospels, Acts, and 13 epistles of Paul were immediately received, copied and disseminated. This includes Greek copies as well as near immediate translations into other languages.