Why Trace Back the Story of the Gospels?

After the death and resurrection of Jesus people were trying to understand what had happened.
This is reflected in the early speeches in Acts as Peter and others they looked back at key points in the gospel story. It is reflected in the presentation of Luke the writer.

There were key questions that related to why such a person as Jesus was crucified. Who was responsible? How did they "pull off" this execution? What was the sequence of events?

Mark and Matthew show Jesus' forgiveness of the ointment woman as a trigger to his betrayal by Judas. But Luke says
'The chief priests and the scribes were trying to work out how they might destroy him for they were afraid of the people. And Satan entered into Judas......'(Luke 22:1-3)

Then after Jesus was captured Luke says
'When day came the body of elders of the people were assembled and (also) both the chief priests and the scribes. They led him away to their council.' (Luke 22:66)
This meant the members of the council had been contacted during the night and they were assembled very early in the morning "When day came" This 'multitude' of the Council then led Jesus before Pilate who sent him on to Herod who then sent him back to Pilate.

Luke then writes 'So Pilate calling together the chief priests and the leaders and the people' (Luke 23:13)
It appears from this that the "multitude" of Council members were waiting around. When Pilate called them back it was this crowd rather than ordinary Jews who called for the death of Jesus.

Luke shows ordinary Jews grieving for Jesus.
'Following behind them was a great multitude of the people and a crowd of women who mourned and lamented for him.' (Luke 23:27) At the crucifixion scene 'The people stood (there) looking. And the rulers were also there scoffing.'
(Luke 23:35)

Luke's angle on 'who was responsible' was picked up in his account of two disciples on the way to Emmaus. They unwittingly told the resurrected Jesus "The chief priests and our rulers delivered him to the jugement of death and crucified him." (Luke 24:20)

In the Acts of the Aposles Luke records Peter as saying "And now brothers. I know that it was because of ignorance that you acted (c/f denying Jesus) and it was also (because of) your rulers" (Acts 3:17)