For one thing, Moltmann followed up on his earlier Theology of Hope by continuing what today we’d call theopoetics. That is, Moltmann broke away from the staid German prose of theologians like Karl Barth and Wolfhart Pannenberg, choosing instead to write in a more freeform and experimental style. This, I think, set the stage for many Western theologians — particularly feminist theologians like Catherine Keller and Kathryn Tanner, who have written in even more open, experimental ways.
Most significantly, CG emphasized the pathos of God. For Moltmann, the Trinity is a dialectical event, and the death of Jesus causes a rupture in the eternal relationality that defines the godhead. In turn, “we participate in the eschatological life of God by virtue of the death of Christ. God is, God is in us, God suffers in us, where love suffers.”