When the people realized Jesus had left Capernaum, they followed him from the shoreline (Luke 9:11). Mark even tells us that at least some of the people were able to reach Bethsaida before Jesus (Mark 6:33-34). When he went ashore and found the people, Jesus had compassion upon them and received them and preached the Kingdom to them and healed many of their diseases (Luke 9:11; Mark 6:34). As the day drew on, however, the Apostles wanted Jesus to send the people away, because there was no food readily available at that place (Luke 9:12). It was a deserted area, probably used for grazing sheep or cattle.
Nevertheless, Jesus told the disciples that they should feed the people, and, of course, the Apostles were astonished with what seemed to them to be an illogical idea (Luke 9:13). There were 5000 men (besides women and children – see Matthew 14:21), and this was realized when the disciples had the people sit down in groups of 50s and 100s (Luke 9:14-15; cf. Mark 6:40). Afterward, Jesus took the five barley loaves and the two fish, which is all the food they had, and he blessed them and divided the supply among the Apostles to set before the people (Luke 9:16; cf. John 6:9, 11). The Apostles did as Jesus commanded, and when everyone had eaten and were satisfied, the disciples gathered the leftovers and filled twelve baskets (Luke 9:16-17).
The reason this particular miracle appears to be so important is that it is one of the few events that is recorded in all four Gospel records. According to the fourth Gospel account, the miracle of feeding the 5000 occurred near the time of Jesus’ second Passover (John 6:4). This Gospel narrative records three Passovers occurring in Jesus’ public ministry, here in 29 AD (John 6:4), the first in 28 AD (John 2:23), and the final Passover in 31 AD (John 13:1; cf. John 18:39). A fourth Passover in 30 AD is implied in Luke 13:1, where we are told Pilate had mingled the blood of the people with the blood of their animal, which they brought to sacrifice at the Temple. Josephus tells us this event occurred during the Passover season. Yet, this Passover season shows Jesus already in Bethany (cf. Luke 10:38), but in the final Passover of 31 AD Jesus first went to Jerusalem, then to Bethany. Therefore, Jesus march toward Jerusalem at this time (Luke 9:51) cannot be the one that ended in his crucifixion, because on his final march to Jerusalem, Jesus entered Jerusalem before he entered Bethany (Luke 19:28-29, 37-38; cf. Mark 11:11).
Jesus empathized with the people that gathered unto him at Bethsaida, because they were like sheep without a shepherd (Mark 6:33-34). Many in the multitude would have been John’s disciples, and now they were without their leader. They were looking to Jesus to replace John in their hearts and minds.
Once the people realized what Jesus had done, feeding about 20,000 people (including women and children) with merely five barley loaves and two fish, they wanted to make him king. In other words, they wanted to crown their Messiah (John 6:9, 14-15). The whole idea of making Jesus a king was preposterous. Only God can do that, and Jesus had to die and rise from the dead to be declared the Messiah (cf. Acts 13:32-34). Jesus had come to this deserted place near Bethsaida in order to get out of the reach of Herod Antipas and defuse the whole matter of his being thought of as a messiah who wished to destroy Herod’s government (cf. John18:36).
Herod wanted to see Jesus in order to clarify what the people had been saying about him. Certainly, he knew John had been announcing the coming of the Messiah, so, if the people were allowed to fulfill their desire to crown Jesus, this would substantiate Herod’s suspicion that Jesus was dangerous to his government. Jesus’ Kingdom is not of this world (John 18:36). He has no desire to usurp the authority given to the kings of this world, because they rule by the authority of God, and to resist them, even Herod Antipas who had beheaded God’s servant, John, would mean that Jesus was resisting God, his Father (cf. Romans 13:1-2).
Therefore, Jesus sent his disciples away by boat, while he retreated into the mountains (John 6:15-17). When the people discovered Jesus had left them in Bethsaida for Capernaum, they followed, but Jesus defused the situation in the synagogue in Capernaum (John 6:59) by speaking to the people in terms they couldn’t understand. In fact, Jesus was so misunderstood that those people, even John’s disciples, followed Jesus no longer (John 6:53-66).
 See: Antiquities of the Jews; Book 18; Chapter 3, paragraph 2 (cf. Wars of the Jews; Book 2; Chapter 9, paragraph 4)