How God can allow his Messiah to be a descendant of immoral people i.e. Judah and Tamar, David and Bathsheba? Hadn’t scribes fabricated these immoral tales?

Good question. One of the beautiful things about Christianity is that Jesus is the descendent of imperfect people.  In fact, when Matthew recorded the genealogy of Jesus, he went out of his way to mention gentile women and “sinners,” such as Tamar, Rahab, Ruth, and Bathsheeba.  David was a man after God’s heart, yet he was guilty of adultery, of deceit, and he was responsible for Uriah’s death.  No human being is without sin.  All of us are sinners.  I do not know about you, but I am guilty of having done immoral acts.  Jesus was the Son of God, but also the son of man, and being the son of man, he was the child of sinners.  This is the beauty of the incarnation.  Christians are not ashamed that Jesus is descended from sinners. We are thankful that Jesus died for sinners.  No, these are not fabricated stories.  Why would Jewish scribes fabricate negative stories about their fellow Jews?  Ancient people did not do this, but the histories in the Bible reflect reality—which is that all humans are flawed, and all humans need God in their life.

John Oakes