Although Lord Buddha was an incarnation of Krsna, he did not speak about God, for the people were unable to understand. He simply wanted to stop animal-killing
"Śrīpāda Śaṅkarācārya has given his interpretation and imaginary meaning. It does not actually appeal to the mind of any sane man. He has done this to convince the atheists and bring them under his control."
Śrīpāda Śaṅkarācārya's propaganda opposed the atheistic philosophy of Buddha. Lord Buddha's intention was to stop atheists from committing the sin of killing animals. Atheists cannot understand God; therefore Lord Buddha appeared and spread the philosophy of nonviolence to keep the atheists from killing animals. Unless one is free from the sin of animal-killing, he cannot understand religion or God. Although Lord Buddha was an incarnation of Kṛṣṇa, he did not speak about God, for the people were unable to understand. He simply wanted to stop animal-killing. Śrīpāda Śaṅkarācārya wanted to establish the predominance of one's spiritual identity; therefore he wanted to convert the atheists through an imaginary interpretation of the Vedic literatures. These are the secrets of the ācāryas. Sometimes they conceal the real purport of the Vedas and explain the Vedas in a different way. Sometimes they enunciate a different theory just to bring the atheists under their control. Thus it is said that Śaṅkara's philosophy is for pāṣaṇḍas, atheists.