John 6:2

‘And a huge crowd were following him because they were seeing the signs which he was performing on those who were sick.'

This very description demonstrates that He had already performed many miracles of healing in Galilee which are not mentioned by John elsewhere, and that there must have been some considerable ministry (unmentioned in John) in order to build up His popularity. It assumes a wide Galilean ministry without mentioning it.

As he regularly does, John brings out that the crowds were following Jesus for the wrong reason. They were sign seekers, not believers. The more they saw the more they wanted. They were looking for a great spectacle. This is preparatory to what follows (their final response in John 6:15). Nevertheless their belief was strong enough to bring them to this lonely place away from civilisation.