Because He could. Who are we, as mere humans, to judge or place limits upon God?
One of the proofs of the power of God is that He can bring forth perfection from imperfection.
why would God put his only Son in a sinfull woman
Because He could. Who are we, as mere humans, to judge or place limits upon God?
Great question, which can be turned around easily - who are we to think God would not/could not create a woman to be the prototype of a new Eve, sinless from conception, but human in every other way - so as to prepare her to be the spotless vessel for God’s Son Jesus to come into the world?