To them it was revealed, that not to themselves, but to you, did they minister these things, which now have been announced to you through those who preached the Gospel to you by the Holy Spirit sent out from heaven; which things angels desire to look into.
So here's the thing that God just sort of kept secret; His plan of grace and redemption through Jesus Christ. Even the angels desired to look into these things that were being ministered by the Holy Spirit through the apostles.