According to the torah of moses Jewish understood that God is only one, so they wouldn’t expect anyone to identify oneself to be equal with God, that’s why they persecuted Jesus.
The Jewish people were expecting their “Messiah” to come as a King dressed in beautiful clothes and have high ranking. They did not expect the true Messiah to be born in a manger and live alongside the broken and poor.
This was a reference to God and his coming from the old testament. They the savior was coming. They just weren’t expecting someone like Jesus. They were expecting someone of higher social class.
It proves that Jesus was claiming to be God before his crucifixion and is why they persecuted Jesus
It was an acknowledgment that Jesus was one with His Father, that He really was God. The priest did not believe Jesus’ affirmation (or didn’t want to believe) that He really was Who He claimed to be, but the timing of this encounter squarely places this prior to the death of Jesus on the cross and absent of manipulation by later observers.
If the “church” invented this idea then why would the priest have ripped his garment? He found this confrontation with Jesus so blasphemous that he tore his garments.
The ripping of the garments by the priest speak to the fact that Jesus was claiming Deity and the priest took very seriously this claim Jesus made. He was claiming to be equal with God and this all happened before he was crucified. The reactions from his enemies prove he had made claims to be God, they considered it blasphemy, and it angered them and likely frightened them as well. They were witnesses to his claims and their actions proved they had heard what he had said. It would have been blasphemy if it were not true.
The priest’s reaction to Jesus’s answer shows that the priest understood Jesus was telling him that he is equal to God and is divine in nature.