Why do the Jews deny Jesus?

Answer 1

Because they were afraid that they would be crucified as well.

Answer 2

Judas didn't deny knowing Jesus. Peter did. He denied knowing Jesus out of fear of being arrested.

Answer 3

The phrase "deny Jesus" is just a bit loaded. Many Jews admit that there quite probably was a historical Jesus who attracted a following and was likely crucified by the Romans. Jews find most of what Jesus taught in the gospels to be perfectly reasonable and in line with the school of Phariseeic thought that eventually gave rise to modern Judaism. (There were other schools of Pharisees that disagreed, and Jesus' negative comments about Phariseeic legalism closely parallel some of the vitriolic comments the different schools had to say about each other.) A few of Jesus' teachings are out there. His opposition to divorce is and his "turn the other cheek" teaching are both relatively extreme -- perhaps on opposite extremes. The big problem Jews have is with claims of the divinity of Jesus. Judaism is strongly monotheistic, holding that the entire idea of God incarnate is utterly unacceptable idolatry. There's no evidence that Jesus claimed to be God incarnate or ever taught anything like trinitarianism, but the doctrines of trinitarianism and incarnation were clearly articulated within the first generation after the crucifixion, and the majority of Jews rejected these out of hand.