Later, during the second two thousand years, when the vessels of ḤaGaT and all the souls were selected from the world, the souls were in fact still very pure, for the vessels of ḤaGaT are at a lofty level, close to that of ḤaBaD (see the introduction to the Zohar, p. 6, s.v. uma). Still, the lights in the world were still covered, due to the lack of vessels from the chest down, both in terms of the world and the souls.
In our generation, the essences of the souls are at the lowest level of all. They could not be selected for sanctity until today. Yet, they still perfect the Partzuf of the world and the aspect of vessels of the souls, and only they can complete this task. Now that the vessels of NaHY are perfected, all the vessels possess a head, middle, and end in the Partzuf. Hence, entire levels of lights flow to the head, middle, and end, to the extent that they are worthy, i.e., perfect NaRaN, as discussed. Only with the perfection of these lower vessels can the upper lights be revealed, not before.