Pew Research points to about 1.6 million Jews who have converted to Christianity in the US alone. Specifically Protestant. A survey in Russia points to about 17% of Jews being Christian, which is impressive because practicing Jews account for only about 31% with the remainder being atheist (27%) or non-religious (25%). The numbers in Israel are big enough to promote anti-missionary efforts as is happening in the States and other parts of the world. With this in mind I am glad you chose the word "many" and not "all." It was the Jews who preached the gospel to the gentiles. The bible says salvation is to the Jew first and then the Greek. That's bible. A Jew does not stop being Jewish when he/she believes in Jesus. Believing in Messiah is one of the most Jewish things to do. So, why do some Jews reject Jesus? The same reasons some gentiles reject Jesus. The hardness of our hearts!