Then they said to Him, “What shall we do, that we may work the works of God?”
Jesus answered and said to them, “This is the work of God, that you believe in Him whom He sent.”(John 6:28-29) NKJV
Jesus makes the claim that he’s sent from God and that the work of God is to believe him who has been sent. The people naturally balk, and ask for a sign from Jesus which would confirm his claim.
They unwittingly present the example of Moses feeding the Israelites with manna in the wilderness. That sets Jesus up to be able to show the people that they don’t have a clue what they’re talking about, nor do they understand Moses. It’s somewhat of a precursor to the great speech given by Stephen, right before he got stoned to death, in which he responded to a similar ill-conceived challenge regarding Moses.
The people are accustomed to being taught the law and the prophets. They think that they need a simple instruction, or rule, that they can follow. A check list of tasks to do everyday by which religious observances they can be assured that they’ll have everlasting life.
Jesus has something much simpler and says: believe in me. The people don’t get it, believe in what? Who? They don’t know how to believe in him, they don’t know what to believe in. There is a chasm of understanding. Then he demonstrates the seemingly impossible feat of making food for 5,000 people materialize out of thin air. Later that evening there is a tempestuous storm. Here comes Hypothesis 37.