I'm shocked at Bart Ehrman's lack of scholarly appraisal, of why Saul taught that Isaiah 53 was fulfilled by Christ; it wasn't some random ideas made up by the Christians.
Also shocked at the lack of historical acknowledgement that the early Ebionite Church with James the Just, didn't teach that Christ came to die as a sin sacrifice, which is referenced at the start of the Book of Acts.
Paul rewrote the Gospel when he made up Christianity (Acts 11:25-26), and Simon joined him - who Yehoshua/Yeshua/Immanuel called "petros" to fulfil prophecy of the 'stumbling stone' (Zechariah 3:9, Isaiah 8:14), and that is where the Christian Church got their atonement ideas from.
In Matthew 15:1-9 & Mark 7:1-13 Yeshua is challenging the Sanhedrin for claiming that the prophets deaths counted for atonement (Matthew 23:27-38), and he said in the Parable of the Wicked Husbandmen that they'd do the same about him (Matthew 21:33-46, Mark 12:1-12, Luke 20:9-19).
I can't believe Bart also used a standard Christianized view point for Yeshua's usage of the word "Ransom", and doesn't use an academic standard citing the Biblical Laws & statements.
No one can pay God, and God doesn't accept Ransom (Psalms 49:7); so Yeshua wasn't claiming that "ransom" meant he was a human sacrifice, and especially not 'the First Born Son given for the sins of your transgressions' (Micah 6:6).
At the Last Supper the consensus in the Synoptic Gospels is Yeshua said "his blood will be spilled for many" - which it was; yet inserting that meant he was declaring he is a human sacrifice, is making him contradict the Hebraic legal standards.
I can understand that Bart Ehrman used to be a Christian, and so is still indoctrinated by John, Saul, & Simon petros's Pharisaic conclusions, yet it isn't a secular academic understanding of what is being stated, it is making it fit with Christendom.
Yeshua gives a clear itinerary of the eschatology in Matthew 24, Mark 13, Luke 21: first the 2nd temple destruction ("not when he came back"), then a time of the Exile among the Gentiles, then Judgement Day coming on the whole of mankind as Betelgeuse goes supernova, and after the Messianic Age - therefore it isn't failed prophecy, as it was all fulfilled back then; there are many things still to be fulfilled soon, as we will see as all Nations gather against Jerusalem.