Christianity evolved from Judaism, but the ideological split happened in the course of two generations. Reformation was also a process that took about 40 years and it created two different branches of Christianity. Another major issue for Judaism and its identity was the Jewish war in 70AD that had a profound effect on the development of the Jewish identity. Prior that event, Jewish faith and culture was deeply integrated in the Greco-Roman culture and their faith was considered as equal. Jewish revolts in 70AD and later 115 cemented their beliefs and national identity due several factors: Jews were considered as a hostile element in Roman society, rabbis were executed through the empire, and Jewish holy books were banished.
While Christianity was also oppressed, their identity development was different from the Judaism. Certainly after 70AD the split between these two groups was permanent and irreconcilable, but for another 50 years there were Jewish Christians as can be seen from contemporary writings. Ignatius who died in 107AD pressured these Jewish Christians to give up their Jewish customs. What I have read, the split had happened between 70AD and 115AD.