Jesus" response to people, in contrast, was not to put His trust (Gr. pisteuo) in them. He knew people to be essentially untrustworthy. He knew that the initial enthusiasm and faith based on miracles that some people manifested would evaporate. Another view is that these were genuine believers who "were not ready for fuller disclosures from the One they had just trusted." [1] Some who initially believed on Jesus turned against Him later ( John 6:15; John 6:60; John 6:66). He did not place His destiny in the hands of any others, though some of the Jews in Jerusalem were willing to place their lives in His hands (cf. John 10:14-15). Moreover He did not commit Himself to anyone, in the sense that Jesus was not dependent on human approval. [2][source]
John may have meant that Jesus knew the nature of human beings (cf. 1 Samuel 16:7; Psalm 139; Jeremiah 17:10; Acts 1:24), not that He knew the thoughts of every person He encountered. The Great Physician could read people better than any human doctor can diagnose symptoms. [3] Besides, Jesus was a prophet, and prophets often demonstrated supernatural insight. On the other hand, John could have meant that Jesus, as only God can, knew the hearts of all people ( 1 Samuel 16:7; 1 Kings 8:39). The following two chapters particularly illustrate the truth of both of these statements: Jesus had great human insight as well as divine insight. [source][source][source]