The grave was secured by the Romans with discretion by the Pharisees. This was very unusual in the 1. Romans were the enemies of the Pharisees and 2. Romans normally didn’t care what happened to a body after execution – usually discarding them in a pit with other dead and decaying prisoners.
Most unique to me is that the way it was set up, there is no way to explain the disappearance of the body of Christ except for resurrection. No theft. No mystery.
Joseph of Arimathea secured the grave. Jesus was laid in a tomb that belonged to him. Jesus was crucified, so his body most likely wouldn’t have wound up in a private tomb. He wound up in a rich man’s tomb, with a stone in front with a seal, and guards to keep watch.
Joseph of Arimathea secured Jesus’ grave site. Most individuals of that time who were crucified were placed into mass graves without any way of knowing who was in the graves. Family tombs were normally reserved for only the wealthiest families of that time.
The Roman soldiers secured the tomb. Yes, they did it to stop Jesus body from being taken. The Roman seal being placed on the tomb and the Roman guard being stationed there.