In Bhagavad-gita (4.8) also it is said that the Lord appears just to give protection to the devotees and to annihilate the nondevotees. The nondevotees are found in the material world, not in the spiritual world; therefore, when the Lord wants to fight, He has to come to this world. But who will fight with the Supreme Lord? No one is able to fight with Him! Therefore, because the Lords pastimes in the material world are always performed with His associates, not with others, He has to find some devotee who will play the part of an enemy. In Bhagavad-gita the Lord says to Arjuna, My dear Arjuna, both you and I have appeared many, many times in this material world, but you have forgotten, whereas I remember. Thus Jaya and Vijaya were selected by the Lord to fight with Him in the material world, and that was the reason the sages came to see Him and accidentally the doorkeepers were cursed. It was the Lords desire to send them to the material world, not perpetually, but for some time. Therefore, just as on a theatrical stage someone takes the part of enemy to the proprietor of the stage, although the play is for a short time and there is no permanent enmity between the servant and the proprietor, so the sura janas (devotees) were cursed by the sages to go to the asura jana, or atheistic families. That a devotee should come into an atheistic family is surprising, but it is simply a show. After finishing their mock fighting, both the devotee and the Lord are again associated in the spiritual planets. That is very explicitly explained here. The conclusion is that no one falls from the spiritual world, or Vaikuntha planet, for it is the eternal abode. But sometimes, as the Lord desires, devotees come into this material world as preachers or as atheists. In each case we must understand that there is a plan of the Lord. Lord Buddha, for example, was an incarnation, yet he preached atheism: There is no God. But actually there was a plan behind this, as explained in the Bhagavatam.