How did the disciples' behavior change from before the crucifixion to after the resurrection?
Before the crucifixion, the eleven disciples scattered like frightened chicks, fearing for their lives. After the resurrection, Peter and the other men became bold and afraid of nothing. Their dramatic change in attitude and boldness, especially seen in Peter and John, testified to the resurrection and its power.
Les explains that if anything proved the resurrection and its power, it was the change of attitude of those 11 men. Before His resurrection, at His crucifixion, they scattered like a bunch of little chicks, scared to death for their life. But after His resurrection, Peter and those men are afraid of nothing. He also notes the boldness of Peter and John, showing that this transformation was visible and striking. The contrast is between fear-driven scattering before the resurrection and fearless boldness after it.