The cosmic manifestation to give another chance to the conditioned souls who were dormant in forgetfulness. The cosmic manifestation gives the conditioned souls a chance to go back home, back to Godhead, and that is its main purpose. The Lord is so kind that in the absence of such a manifestation He feels something wanting, and back to Godhead, thus the creation takes place. Although the creation of the internal potency was manifested, the other potency appeared to be sleeping, and the Lord wanted to awaken her to activity, just as a husband wants to awaken his wife from the sleeping state for enjoyment.
Reference: The cosmic manifestation to give another chance to the conditioned souls who were dormant in forgetfulness. The