Here is another video of Carrier explaining how Christianity started out from Judaism beliefs in the coming Messiah Christ.
https://www.youtube.com/watch?v=gHdLgPKv-Nc
Both Early Christianity and Early Rabbinic Judaism were far less orthodox and less theologically homogeneous than they are today; and both religions were significantly influenced by Hellenistic religion and they also borrowed allegories and concepts from Classical Hellenistic philosophy[113] and the works of Greek-speaking Jewish authors of the end of the Second Temple period before the two schools of thought eventually firmed up their respective "norms" and doctrines, notably by diverging increasingly on key issues such as the status of "purity laws", the validity of Judeo-Christian messianic beliefs, and, more importantly, the use of Koine Greek and Latin as sacerdotal languages replacing Biblical Hebrew.[