One of the most human of our bad traits is to almost universally think poorly of those who are not of our group. This may be behind Jacob’s discussion of the wickedness of the Jews that was so bad that they would crucify their God. It is a sentiment that began to develop in early Christianity after the destruction of the temple and the irreparable rift between Jews and Christians. It is probable that this is the only way a people who are uninvolved in the actual historical conditions could imagine that God himself would walk among his people, as a mortal, and as a mortal, be ignominiously killed.
While the text clearly says that the Messiah would be crucified, we cannot tell if Jacob’s audience would have any understanding of what that meant. It is probably the result of the translation, since Joseph clearly knew the terrible method by which Jesus was killed. The import of the message was that he would be killed, not the method.