The overemphasis for the importance of the crucifixion or death of Jesus on the cross was not put in place until the era of Constantine. Historically, the issue of whether Jesus was or was not on the cross and crucified was settled around 148 AC according the Roman church's satisfaction. In addition, the idea of Jesus being crucified was believed by certain Jewish-Christian sects for various reasons from the time of the actual crucifixion event. Furthermore, the declaration that Jesus rose from the dead was bound to cause trouble to those who lacked a deep comprehension in religious matters.
The reasons for this are varied. It must not be forgotten, however, that during many decades the forming 'church' and its multitudinous sects were undergoing excruciating turmoil within and outside its ranks and this caused a lot of confusion to enter into the mix.
Before the actual formation of Christianity, as a distinct religious movement, several ideas were floating around and one of them was that Jesus was not of the 'flesh' but a spiritual being. To counteract that idea, the notion that Jesus was actually crucified took concrete shape as if to prove his real existence and that he was not just an 'angelic' figure but a real person.
The truth concerning the crucifixion event is astounding but only when an honest approach to all of the scriptures and a truthful look at history is applied. That is the truth but acceptance of this truth is quite another matter indeed