Replies

Verses. 59 on tell exactly why they left,

Yes....but it really starts at v64

64“But there are some of you who do not believe.” For Jesus knew from the beginning who they were who did not believe, and who it was that would betray Him. 65And He was saying, “For this reason I have said to you, that no one can come to Me unless it has been granted him from the Father.” 66As a result of this many of His disciples withdrew and were not walking with Him anymore.

Notice Peter's answer to Christ:

67So Jesus said to the twelve, “You do not want to go away also, do you?” 68Simon Peter answered Him, “Lord, to whom shall we go? You have words of eternal life. 69“We have believed and have come to know that You are the Holy One of God.” John 6:67-70 NASB

Essentially the same answer given previously:

15He said to them, “But who do you say that I am?” 16Simon Peter answered, “You are the Christ, the Son of the living God.” Matthew 16:15-16 NASB

Martha's reply to Jesus when discussing Lazarus:

25Jesus said to her, “I am the resurrection and the life; he who believes in Me will live even if he dies, 26and everyone who lives and believes in Me will never die. Do you believe this?” 27She said to Him, “Yes, Lord; I have believed that You are the Christ, the Son of God, even He who comes into the world.” John 6:25-27 NASB

John's account of the Samaritans who believed after hearing Him.

39From that city many of the Samaritans believed in Him because of the word of the woman who testified, “He told me all the things that I have done.” 40So when the Samaritans came to Jesus, they were asking Him to stay with them; and He stayed there two days. 41Many more believed because of His word; 42and they were saying to the woman, “It is no longer because of what you said that we believe, for we have heard for ourselves and know that this One is indeed the Savior of the world.” John 4:39-42 NASB

Jesus addressing the unbelieving Jews:

24“Truly, truly, I say to you, he who hears My word, and believes Him who sent Me, has eternal life, and does not come into judgment, but has passed out of death into life. John 5:24 NASB

Jesus addressing Nicodemus:

4Nicodemus said to Him, “How can a man be born when he is old? He cannot enter a second time into his mother’s womb and be born, can he?” 5Jesus answered, “Truly, truly, I say to you, unless one is born of water and the Spirit he cannot enter into the kingdom of God. 6“That which is born of the flesh is flesh, and that which is born of the Spirit is spirit. 7“Do not be amazed that I said to you, ‘You must be born again.’ 8“The wind blows where it wishes and you hear the sound of it, but do not know where it comes from and where it is going; so is everyone who is born of the Spirit.”

9Nicodemus said to Him, “How can these things be?” 10Jesus answered and said to him, “Are you the teacher of Israel and do not understand these things? 11“Truly, truly, I say to you, we speak of what we know and testify of what we have seen, and you do not accept our testimony. 12“If I told you earthly things and you do not believe, how will you believe if I tell you heavenly things? 13“No one has ascended into heaven, but He who descended from heaven: the Son of Man. 14“As Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up; 15so that whoever believes will in Him have eternal life.

16“For God so loved the world, that He gave His only begotten Son, that whoever believes in Him shall not perish, but have eternal life. 17“For God did not send the Son into the world to judge the world, but that the world might be saved through Him. 18“He who believes in Him is not judged; he who does not believe has been judged already, because he has not believed in the name of the only begotten Son of God. 19“This is the judgment, that the Light has come into the world, and men loved the darkness rather than the Light, for their deeds were evil. 20“For everyone who does evil hates the Light, and does not come to the Light for fear that his deeds will be exposed. 21“But he who practices the truth comes to the Light, so that his deeds may be manifested as having been wrought in God.” John 3:4-21 NASB

All of these passages, save for the one on Lazarus, were before the Bread of Life discourse. All say we have to believe in Him. There is no mention of eating/drinking flesh or blood by Christ to these people.

Why?

Did He misinform them or lead them astray?

No.

Again, context is key in understanding Scripture.

John uses the word believe on one form or another some 81 times. The majority of them [I haven't counted], related to believing in Christ for eternal life.

28Therefore they said to Him, “What shall we do, so that we may work the works of God?”

29Jesus answered and said to them, “This is the work of God, that you believe in Him whom He has sent.” John 6:28-29 NASB

We come to Christ through faith in Him.