“Read John 6 and tell me why those disciples walked away from Christ at that time.”
It probably had to do with there concrete materialistic way of thinking at the time. Remember in John 3 Nicodemus had trouble understanding Jesus teaching of rebirth, “How can one enter into his mother’s womb and be born again?”. In John 4 the Samaritan woman had trouble with understanding the “water” that Jesus was promising to give, “give me this water tat I thirst not and don’t have to come here again”.
Now in John 6 the crowds, including fringe disciples were making the same error, not understanding that Jesus was speaking metaphorically about spiritual things when He spoke of eating and drinking His body and blood.
And then Jesus explains to Nicodemus. As for the Samaritan woman it sounds like she realizes that Jesus, Himself is the Living Water by the time their discourse is finished.