Jesus spent more than 3 years in His earthly ministry. The priest and pharisees were responsible for His arrest and crucifixion. He was crucified by the Romans according to their law.
Is it but fitting that He would show Himself to these people after His resurrection so that they would know that their efforts were of no value and He is really the son of God? His disciples would no longer have a hard time proving to them that Jesus was really alive.