Krsna has three main energies: The spiritual energy (or internal potency), the material energy (or external potency), and the marginal energy (the individual souls, who can choose between staying under the internal energy, or the external energy).
The internal potency composes all the spiritual planets and everything else that exists there. There everything is eternal, composed of eternity, knowledge, and bliss. It equals 75% or more of the creation, and 90% or more of all souls live there. All souls come originally from this spiritual potency and thus are eternally connected with Krsna with a bound of love. This love for Krsna, or Prema, is already inside the soul. More specifically, it is part of the soul, and can’t be separated or lost. As Sri Caitanya Mahaprabhu explains:
nitya-siddha kṛṣṇa-prema ‘sādhya’ kabhu naya
śravaṇādi-śuddha-citte karaye udaya
“Pure love for Kṛṣṇa is eternally established in the hearts of the living entities. It is not something to be gained from another source. When the heart is purified by hearing and chanting, this love naturally awakens.” (CC Madhya 22.108)
However, this natural love for Krsna that is inside the soul becomes covered when the soul comes in contact with the material energy. When we come to this material world, our real spiritual self is covered with many material layers, such as the false ego, intelligence, mind, and senses that form our subtle body. This subtle body is then covered by the gross body. With so many covers, our eternal spiritual form becomes covered and our natural love for Krsna is temporarily suppressed. Because of all these coverings, we forget what we are, and start thinking that we are men, women, animals, plants, or demigods in this material world.
By following the process of devotional service, our natural love for Krsna is gradually awakened, and with this, all the material coverings are gradually destroyed, and our eternal spiritual body becomes visible, just like the sun when clouds are cleared.
How and why the soul falls into the material world is a very complicated question. However, there are two important points to understand, according to Prabhupada’s teachings:
1- Love for Krsna is part of the soul and is present even now. It doesn’t have to be gained from another source but simply uncovered. For this, we need to remove the material contaminations from our hearts by following the process of bhakti and associating with sincere devotees.
2- The second is that we come to this material world by free will, or in other words, due to our own choice. Krsna didn’t want us to come here, and now He wants us back. That’s the reason He follows us life after life as Paramatma. No one else does that for us. Krsna is thus our true friend. When we understand that and start to again look for Him, we start our way back home.
These points are repeated by Prabhupada in numerous passages. They are very clear in his teachings. Take this passage from the 4th canto for example (4.28.52-55), where Paramatma speaks to King Puranjana in his rebirth as a woman:
“Who are you? Whose wife or daughter are you? Who is the man lying here? It appears you are lamenting for this dead body. Don’t you recognize Me? I am your eternal friend. You may remember that many times in the past you have consulted Me.
My dear friend, even though you cannot immediately recognize Me, can’t you remember that in the past you had a very intimate friend? Unfortunately, you gave up My company and accepted a position as enjoyer of this material world.
My dear gentle friend, both you and I are exactly like two swans. We live together in the same heart, which is just like the Mānasa Lake. Although we have been living together for many thousands of years, we are still far away from our original home.
My dear friend, you are now My very same friend. Since you left Me, you have become more and more materialistic, and not seeing Me, you have been traveling in different forms throughout this material world, which was created by some woman.” (the material energy)
There are Vaishnava schools that have other opinions, and disagreement is of course the nature of this material world, but when we come to the teachings of Srila Prabhupada these two points are very clear. Without accepting these points, one will eventually come to the conclusion that Prabhupada was teaching only the ABCD or that he was telling lies with the goal of making his books easier for the Western audience. Both ideas are of course clearly offensive and will block one from understanding the real meaning of his books.