Luke states that, at first, they were blind to the fact that it was Jesus who joined them (Lk. 24:16). But following His teaching them, using the Old Testament (The Law, The Prophets, and The Writings - Lk. 24:26-27), that their Messiah had to suffer death, He opened their eyes so that they could recognize Him (Lk. 24:31). He immediately disappeared, and they hurried back to Jerusalem to tell the rest of the disciples of their encounter with the risen Lord (Lk. 24:31-35). While they were testifying, Jesus appeared in their midst, and still, they could not comprehend it all; they were afraid (Lk. 24:37). Jesus reassured them it was He (Lk. 24:38-43).
Jesus opened their understanding (Lk. 24:45)! He reminded them that He had told them before He was crucified, that it was going to happen (Mt. 20:17-19; Mk. 10:32-34; Lk. 18:31-34; etc.). And again, Jesus taught from the Old Testament, those things which were written of His death, burial, and Resurrection. I am quite certain the passages He showed them included Psalm 22 and Isaiah 53!
Here we are, approximately 2000 years later, and Christianity is the world's largest religion. About two in seven people on this planet of seven billions souls, claims to be Christians. What began with twelve, has grown into a "massive tree" with its "branches" being hundreds of denominations. That sounds wonderful until one reads, with understanding, the parables of the Church Age, found in Matthew Thirteen! There, we find, the Lord taught that His Church would be infiltrated by the enemy: tares (Mt. 13:24-30); birds (Mt. 13:31-32); leaven, that is, false doctrine (Mt. 13:33 c. Mt. 16:6, 11-12); a field of mostly dirt (Mt. 13:44); and bad fish (Mt. 13:47-48)! Yes, the Church has grown in numbers, but many of its members are travelling down the "broad way," saying, "Lord, Lord..."; and are in for a horrible surprise!
Mega-churches are known for watered-down doctrine and compromise of truth!
Many are filled with Laodiceans who do not hear Jesus knocking to get in!