Usually when a leader who is loved by his people is leaving office, it leaves the people with some sorrow because they will miss him/her. In the last council meeting of the former Chairman of the Church of Pentecost, Apostle Professor Opoku Onyinah, in 2018 many of the councilors shed tears because a great leader was exiting. Similarly, the Apostles were gazing into the sky wishing Christ had not left them to heaven.
I assume they were recalling this healing Jesus, the anointed one who made the blind see, the cripple walk, the deaf hear and died to save humanity and how their lives were going to be now that He was gone. Their hearts might have been filled with sorrow at that moment. Their hopes were dashed. Their disappointment might have caused them to forget Jesus’ firm promise of returning for them. Then the angel of God appeared to reassure them that “this same Jesus … will come back.”
Remember that the angel was referring to the resurrected Jesus who had defeated death and hell. The one who appeared among the disciples when they were meeting without using the door, though He was flesh and blood like them. He could not be physically impeded from going where He wanted to go. This same Jesus who ascended into heaven without an aircraft or spaceship will come again. Halleluyah!