The report that Jesus said, "I and my Father are one" comes only in John 10:30, and is not reported as leading directly to his crucifixion.
Nor does the context here & elsewhere suggest Jesus meant anything other than you or I might mean in saying: "when you're talking to me, you're talking to my boss."
In fact, there are different schools of thought on exactly why Jesus was crucified, including one which emphasizes the Romans' political fears that Jews might raise up a new king -- hence the plaque saying "King of the Jews" on his cross, reported by all four gospel writers.
Jesus was put to death for blasphemy. It’s right there in the gospels. If you want to come up to speed on the historicity of His claim before the sanhedrin, I recommend the book “Jesus: God Ghost or Guru” by Hyde & Buell.
As a ferinstance, He claimed to be coming on the clouds of Heaven. Only God comes on the clouds of Heaven. He also said he’d sit at the right hand of Power, which is a claim of equality to God. Both claims are quotes from Daniel.
He also said “Ani Hu”, which gets translated as “I am” or “I am He”, and was too holy to utter in public except by the high priest on a holy day.
And look at the response: let’s put this guy to death for blasphemy, followed by the loud sound of tearing cloth. Even the sanhedrin put out a circular letter saying that they had Jesus killed for blasphemy.
It is among the most best attested events in history.
In fact, there are different schools of thought on exactly why Jesus was crucified,
***There was only one school of thought in the first century. It was shared by the friends and enemies of Jesus — He was put to death for blasphemy. When both sides of a conflict agree to certain facts, it is an established fact of history.
including one which emphasizes the Romans’ political fears that Jews might raise up a new king — hence the plaque saying “King of the Jews” on his cross, reported by all four gospel writers.
***Then you accept that aspect as established history, good. Because in the same historical accounts the jews said they were prevented from putting someone to death. They had lost their sovereignty over Judea when the Romans came. And Romans being who they were, they “reserved the right of the sword and neglected all else”. This loss of sovereignty over Judah was a fulfillment of a bible prophecy in Genesis 49:10. Judah would have self-rule until Messiah came.