The Jews would not have considered Jesus a threat, but insane if he had walked around saying he was God. But it was a threat for Jesus to claim to be the Messiah of God and also walk around doing miracles. Jesus had not been claiming to be God in the flesh and this is why the Jews never asked him at his trial if he was God in the flesh, but instead they asked him about what he had been claiming to be, which was the Messiah. Mark 14:61-62 records the High Priest asking “Are you the Christ, the Son of the Blessed?" And Jesus said "I am.” The High Priest tore his garments and said he deserved to be put to death when Jesus stated he was the Messiah. So we see that the Jews correctly assessed that Jesus had been claiming to be the Christ, and that Jesus indeed said he was the Christ, and also that the Jews thought his claim was worthy of the death penalty.