Jesus is the Messiah son of Joseph in two different steps:
The first step, more genuine: the Christianity started probably as a Joshua cult. And Joshua was already sincerely recognized as the Messiah Son of Joseph.
The second step, more tendentious and artificial: Jesus is said to be son of Joseph via midrash and, in particular, his human judge is Pilate, infamous slayer of the "sons of Joseph" (=the Samaritans).
Without the marcionite invasion, the second step would have been not necessary at all.