According to (orthodox) Judaism, pikuach nefesh does not justify murder or suicide or putting one's life at a greater risk than the person who's life is at risk -to save the person. An orthodox jew is not allowed to enter inside a church or reformed synagogue even to save a life (that is to say,the place where worship takes place. A Jew may enter a room of a reformed synagogue not used for worship.) Chillul hashem (idolatry, blasphemy, etc.) is never allowed even to save one's own skin.
Only 2 Jewish movements survived 70 CE 1. Christianity: based on salvation from Jehovah 2. Pharisaic Jews: based on salvation from Caesar (We have no king but Caesar!) Circa 70* the Pharisees (Rabbi Yohanan) made a deal with Caesar and settled in Yavneh where they adapted laws to fit modern Judaism without beth hamikdash, installing themselves as leaders. Interstingly, dna studies of Ashkenazi jews today show y chromsome comes from a few hundred middle Eastern men from the fertile cresent ( jews ) that married non jewish females no doubt converting them first. Acccording to the studies most Ashkenazi jews are between 23 percent to about 53 percent European (non-Jew dna)
*70 years after the birth of Jesus 40 years after Jesus began his public ministry