Explanation:

The power of God also can accomplish this excellent goal and thus God need not enter directly to do this divine work. But God takes the fascination to do this work directly. Even though the king can get a deer in the forest killed by hunters for food, the king directly goes to the forest for hunting the deer. The hunting gives pleasure to the king directly. The king is interested in the process and not in the final fruit. Similarly, God can change this humanity just by His will. The task of preaching the humanity gives Him nice entertainment. In this task, His direct participation gives Him greatest pleasure as in the case of king in hunting. Brahma Sutra tells the same point (Lokavattu..). Veda (Prajnanam Brahma) and Gita (Jnanitvaatmaiva..) also say that God directly comes to preach the spiritual knowledge. Krishna preached Gita and sages recognized Him as God due to Gita only inspite of His negative maya exhibited. Shankara concentrated on spiritual preaching only. Even other religions say that God comes in flesh as in the case of Jesus, who mainly concentrated on giving the spiritual knowledge. The revision of spiritual knowledge that was already preached by God can be done by God through the liberated souls using His power. Shankara preached all the concept but stressed a portion only in His time due to circumstances. Later on, the other part of His spiritual knowledge was revised by Ramanuja and Madhva, who were liberated souls sent by Him through His power.