Jesus, after His resurrection, trained His disciples over a period of 40 days to realize that He was with them though they could no see Him.
Jesus trained His early disciples to live by His invisible presence. This was crucial in God's purpose - for men and women to live in oneness with Christ who, in addition to rising from the dead, became a life giving Spirit to indwell His believers.
"the last Adam became a life giving Spirit" (1 Cor. 15:45)
Not only did Jesus train the disciples to realize that He was with them though they could not see Him. He also trained them that He was going to be within many of their Christian brothers and sisters as members of His mystical Body.
For this reason, outwardly, the personal appearance may vary. Inwardly the person was joined to Christ, associated with Christ, and indwelt with by Christ. Each member of the NT church had Christ living in her or him and ALL the disciples should treat one another accordingly.
Skeptics have to offer alternative explanations of why a sizable number of Jews suddenly made such changes in long held traditions, Ie. the Saturday main day worship to the
"Lord's Day" - first day of the new week to celebrate the life of Jesus.
Skeptics also have to offer alternative explanations to scores of Jews discontinuing animal offerings in favor of believing that the man Jesus of Nazareth had offered ONE and FINAL sacrificial offering of Himself for all time.
Skeptics can also explain the mention of 500 eyewitnesses of the resurrected Jesus that the Apostle Paul argued could mostly be still consulted with to verify the apostolic teaching of the resurrected Christ -
(First Cor. 15:5-11).
Mass hallucination is unlikely.
That Paul fabricated such a large and mostly available body of eyewitnesses is unlikely.
God is about dispensing the Spirit of Christ into people. Millions have claimed God and Christ became real to them upon opening their innermost heart and spirit to Jesus and the Gospel. In short a vast number of fellow human beings claim that Jesus is available which would be perfectly consistent with what He Himself was teaching.
Preparing His disciples for His death and resurrection He said this:
"But I tell you the truth, it is expedient for you that I go away; for if I do not go away, the Comforter will not come to you; but if I go, I will send Him to you. " (John 16:7)
It is expedient that Jesus ascend physically to the right hand of God somewhere at the peak of all being - in the third heaven. If He did not the Spirit of Reality - the Comforter - the Holy Spirit who is Christ in His pneumatic form, would not come to be IN the disciples.
So after the resurrection Jesus did a number of things to transition His disciples to understand that He was now going to be the Holy Spirit living within their spirit -as He had also promised -
"Jesus answered and said to him, If anyone loves Me, he will keep My word, and My Father will love him, and We [Father and Son] will come to him and make an abode with him." (John 14:23)
We Christians testify that we know Jesus rose from the dead, because this expediency has indeed taken place as He promised. Jesus Christ can come to us and make an abode with us. He can be Christ IN us as the life giving Holy Spirit. T
As the skeptic places all his priorities in physical proofs of Christ's resurrection Christ and God put the right amount of emphasis upon this. And the Triune God put emphasis ALSO on the expediency of the living and available Christ coming to make an abode within His believers. This God deems today as the main witness He wants to the world for the truth of Christ having been raised from the dead.
The skeptic only cares for grandstanding which proved inadequate to really change lives. God was seen on Mt. Sinai for 40 days and the people grew weary and unbelieving, making a golden calf and wanting to return to Egypt.
Grandstanding in a visible way has its limitations. God's priorities were in changed lives of those who grasped the reality of the living and available Son of God.