Complex sentence: For the new atheists, the triumphs of science lead to a belief that God is not necessary and, moreover, that the very foundations of theism are denied by postmodernism since God is merely one socially constructed reality among others.
Split into simpler sentences: For the New Atheists, the triumphs of science lead to a belief that God is not necessary and, moreover, that the very foundations of theism are denied by postmodernism. That is for New Atheists God is merely one socially constructed reality among others.