At that time people were sacrificing the poor animals under the plea of Vedic sacrifice. So demonic persons, they want to do something under the protection of authority. Just like a big lawyer takes the protection of the law book and he makes the law unlawful. Similarly, the demons are so intelligent that they take advantage of scriptural injunction and do all nonsense. So these things were going on. In the name of Vedic sacrifice, they were killing animals like anything.
So Lord became very much compassionate with these poor animals, and He appeared as Lord Buddha, and his philosophy was nonviolence. His philosophy was atheist because he said that, "There is no God. This combination of matter is a manifestation, and you dismantle the material elements, there will be void and there will be no sense of pleasure and pain. That is the nirvāṇa, ultimate goal of life." That was his philosophy. But actually his mission was to stop animal killing, to stop the men from so much sinful activities. So Lord Buddha is also prayed herewith.
So people will be surprised that Lord Buddha is designated as atheist and still the Vaiṣṇavas, they are offering their respectful prayers to Lord Viṣṇu (Buddha). Why? Because the Vaiṣṇava knows how the God is acting for His different purposes. Others, they do not know.
The next avatāra incarnation is Kalki. That is yet to take place. Kalki avatāra will appear at the end of this age, Kali-yuga. The age of Kali-yuga, duration of this age, is still to be, I mean to say, fulfilled in 400,000's of years. So at the end of Kali, that means at the last stage, after about 400,000's of years, the incarnation of Kali will appear. That is predicted in the Vedic literatures, as Lord Buddha's appearance was also predicted in the Śrīmad-Bhāgavatam. And Śrīmad-Bhāgavatam was compiled five thousand years ago, and Lord Buddha appeared about 2,500 years ago.
Therefore about Lord Buddha's appearance it is predicted that at the beginning of Kali-yuga Lord Buddha will appear. There was prediction, and that has actually come to be true. Similarly, there is prediction about Kalki avatāra, and that will also come to be true.
So at that time Lord Kalki's business will be to simply to kill. No instruction. Just like . . . in Bhagavad-gītā Lord Kṛṣṇa gave instruction in the shape of Bhagavad-gītā. But at the end of Kali-yuga, people will be so much degraded that there is no more possibility to give any instruction. They will not be able to understand it. At that time the only weapon will be to kill them.