A seeker of a religious approach to life will inevitably be drawn to the religious system projecting the highest-level “authenticity/legitimacy.” Almost by definition.

Christianity is compelled to hinge its own declared authenticity on the source-authenticity of Sinai (c. 1250 BCE), i.e. the giving of the Torah at Sinai. But Christianity, of course, simultaneously did not/does not want the potential-for-conversion masses or its existing adherents leapfrogging over Christianity directly towards the “original-source,” Judaism.

Thus, the Church Father stratagem has been to grant “authenticity” to “Sinai” while simultaneously taking-the-edge-off of the legitimacy of Judaism per se.

Thus, the Church “parses” the authenticity/legitimacy
of Sinai/Judaism:Sinai—YES; but Judaism—NOT QUITE.
or
Sinai—YES; but Judaism—MAYBE THEN. NOT NOW.

Now, the Church remains with a great deal of difficulty in dealing with the Torah – The Five Books of Moses. Because Church doctrine contradicts Torah doctrine. Essentially, the Church acrobatic-act stratagem would be to simultaneously pontificate that the Torah is both legitimate – and illegitimate. This stratagem is hard to finesse.