In order to establish his doctrine of non-violence, Lord Buddha flatly refused to believe in the Vedas, and thus, later on, Sri Sankaracarya stopped this system of religion in India and forced it to go outside India.
Sri Sankaracarya 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 acaryas. Sometimes they conceal the real purpose 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.
It is stated in Padma Purana:
Lord Siva speaking to Parvati foretold that he would spread the mayavada philosophy in the guise of a sannyasi brahmana just to eradicate Buddhist philosophy. This sannyasi was Sri Sankaracarya. In order to overcome the effects of Buddhist philosophy and spread Vedanta philosophy, Sri Sankaracarya had to make some compromise with the Buddhist philosophy, and as such he preached the philosophy of monism, for it was required at that time. The mayavada philosophers refuse to accept the spiritual body of the Supreme Absolute Person and refuse to accept that the living entity has an individual existence separate from that of the Supreme Lord.
Mayavadi philosophers had propagated the slogan "brahman satyam jagan mithya", which declared that the Absolute Truth was a fact but the cosmic manifestation and the living entities were simply illusions, or that all of them were in fact the Absolute Truth and that the material world and living entities did not separately exist.
Sri Sankaracarya, who preached mayavadi philosophy and stressed the Impersonal feature of the Absolute, also recommended that one must take shelter at the lotus feet of Lord Sri Krishna, for there is no hope of gain from debating. Indirectly Sri Sankaracarya admitted that what he had preached in the flowery grammatical language. The interpretations of the Vedanta sutra cannot help one at the time of death. At the critical hour of death one must recite the name of Govinda.
Then Sankaracarya came and he preached this almost Buddhism. Lord Buddha preached that there is no God there is no soul. This body is combination of matter and if we dissolve this material combination then there is no more perception of misery or happiness. That is nirvana. That is his philosophy. But later on Acarya Sankara, he appeared and he preached that brahma satyam jagan mithya. This bodily combination is temporary, or mithya. He said flatly that it is false. False means... Of course, Vaisnava philosophy, they say temporary. Temporary or false you can take on the same category. But Sankaracarya said that brahma satyam. That spirit soul, Brahman, that is reality, and this external feature of the Brahman, or the body, that is false.
Sri Sankaracarya, by the order of the Supreme Personality of Godhead, compromised between atheism and theism in order to cheat the atheists and bring them to theism, and to do so he gave up the direct method of Vedic knowledge and tried to present a meaning, which is indirect.
It is with this purpose that Sri Sankaracarya wrote his Sariraka-bhasya commentary on the Vedanta sutra.
One may argue that since Sri Sankaracarya is an incarnation of Lord Siva, how is it that he cheated people in this way?
The answer is that he did so on the order of his master, the Supreme Personality of Godhead. This is confirmed in the Padma Purana.