In Matthew 4:18-22, Jesus calls Peter, Andrew, James, and John to be his disciples. All of them immediately leave behind their family fishing business to follow Jesus.
Why did they follow Jesus? They had good jobs. Why did they exchange them for an unpredictable life of economic insecurity? When a scribe requested to follow Jesus, Jesus told him that "[f]oxes have holes, and birds of the air have nests; but the Son of Man has nowhere to lay his head" (Matthew 8:20 NRSV). "There are times when I go homeless, friend," Jesus was saying. "Is that the type of life you really want?" Yet, Peter, Andrew, James, and John not only followed Jesus--they followed him immediately, as in right after he called them. Why?
When I was in college, I had to write an undergraduate thesis for my major, which was religion. A young lady in my seminar wrote about the twelve disciples, and one of her questions was, "Why did they follow Jesus?" I don't entirely remember her answer, but I remembered her question when I was reading Matthew 4-5 for my daily quiet time. I wondered if the Bible contained any answers, and, after much thought, I concluded that it did.
So why did the disciples leave everything behind to follow Jesus? The reason is this: They believed that Jesus was the promised Messiah, the person who would rule Israel and the rest of the world. Both before and after Jesus' death and resurrection, they thought that he was the one who'd restore Israel (Luke 24:21; Acts 1:6). They desired power and influence. James and John exemplified this attitude when they asked to sit beside Jesus in his kingdom (Matthew 20:21).
So did the disciples believe that following Jesus entailed a crown and not a cross? Their view on this seems to have changed over time. When Jesus said that he was going to Jerusalem to die, Peter rebuked him, saying, "God forbid it, Lord! This must never happen to you." That prompted Jesus to call Peter "Satan," then to give his disciples a lecture about taking up their cross to follow him (Matthew 16:21-26). At first, the disciples didn't really anticipate a cross, for Jesus or for themselves.
Later, when James and John asked for thrones next to Jesus in his kingdom, they affirmed their willingness to drink the cup of persecution that Jesus was about to drink (Matthew 20:22). At the Lord's supper, Peter said he'd die with Jesus (Matthew 26:35). The disciples still expected status and prestige in Jesus' kingdom, but they acknowledged the possibility that their deaths could precede that.
But they didn't think that death was a barrier for Jesus. In John 6, when many of Jesus' disciples abandoned him because of his hard teaching, the twelve stuck with him. Jesus inquired why, and Peter responded, "Lord, to whom can we go? You have the words of eternal life" (v 68). For Peter, Jesus as the Messiah had power over life and death. Consequently, they could embrace the possibility of their martyrdom even as they maintained their hope that Jesus would grant them status in his kingdom. Similarly, the death of Jesus himself did not inhibit the faith of the thief on the cross that Jesus was the Messiah. There Jesus was, dying right next to him, yet the thief believed that Jesus would get power once he entered his kingdom (Luke 23:42).
So the disciples followed Jesus because they thought he was the Messiah, and being with the coming king could bring ultimate advantages. But why did they believe that he was the Messiah? The New Testament has some answers on this.
In Luke 5:2-11, there are details about Jesus' calling of Peter, James, and John that are not in Matthew. In that passage, Jesus tells Peter to cast his net into the sea. Peter replies, "Master, we have worked all night long but have caught nothing. Yet if you say so, I will let down the nets" (v 5). Immediately, they caught so many fish that the boat was about to sink! Peter then realized that he was in the presence of a man of God, and his own personal inadequacies became glaring to him. "Go away from me, Lord, for I am a sinful man!" he exclaimed.
And so the miracle may have confirmed for Peter that Jesus was the Messiah. Yet, there are other things to notice. First of all, Peter appears to have already known Jesus, and, second, he calls him "master." Peter was not an official disciple (or, for Luke, apostle) until Luke 6:13-16, yet he still recognized Jesus as some sort of authority. Why?
John 1:35-51 may contain some answers. Peter possibly knew Jesus through his brother Andrew, who initially followed John the Baptist. According to the Gospel authors, John the Baptist recognized that Jesus was the Messiah, and Andrew respected his mentor's opinion. Andrew's regard for Jesus may have rubbed off on Peter, such that Peter called Jesus "master" even when he wasn't a follower. Or perhaps Peter saw something in Jesus that he admired, only he was not yet ready to leave everything behind. But the miracle gave him the extra boost to follow Jesus as the Messiah.
Also in John 1:35-51, we see other disciples receiving Jesus. The passage is not specific about why Philip followed him, but Nathanael was impressed because Jesus saw him (Nathanael) under the fig tree before Philip called him. That must have been some miracle, even though I'm not exactly sure what it was! One minute, Nathanael was asking if anything good could come out of Nazareth. The next minute, after Jesus tells him about the fig tree, he praises Jesus as the new king of Israel.
So Jesus' miracles played some role in convincing the disciples of his Messianic identity. But the Gospels are clear that there is an additional factor, and Calvinists are going to love this: God personally revealed to the disciples that Jesus was the Messiah. Jesus prayed, "I thank you, Father, Lord of heaven and earth, because you have hidden these things from the wise and the intelligent and have revealed them to infants" (Matthew 11:25). When Peter confessed that Jesus was the Christ, Jesus responded, "Blessed are you, Simon son of Jonah! For flesh and blood has not revealed this to you, but my Father in heaven" (Matthew 16:17).
So why did the disciples follow Jesus? A desire for power. Miracles. A respect for John the Baptist. Something about Jesus' personality that seemed worthy of honor. A revelation from God. Most of these were legitimate reasons. Some of them were not. All of them set the disciples on a journey in which God used them profoundly.