In this passage Jesus continues to minister. Because Jesus told people not to tell people who performed their miracles, people are following Jesus in masses and he actually has to preach from a boat so that they don't crush him and his disciples act as bouncers.
Jesus heals demons who know who he is. He is the Son of God and will burn them in hell forever. They know who he is. But at this time, Jesus still does not want to blatantly proclaim himself as the Messiah because he wants people to realize it on their own.
Then he picks disciples. This is when Jesus baffles me. He picks people who otherwise should never work together. He picks Simon the Zealot. This man loves Israel and hates Romans so much that he is alright with killing a Gentile in the name of Israel. Along with Simon Zed, he picks Matthew or Levi, the tax collector, an Israelite who compromises with Rome so much that he takes money from his brothers and takes extra for himself. He has Simon Peter and Andrew, and James and John, more moderate fellows. He has Judas Iscariot who later betrays Jesus, and Jesus picks him anyway.
Then he has the people following him, mostly because he can heal and give free bread, not because they truly love God and want to follow Jesus. Then there are the demons who prove that you can believe in Jesus and still hate him.
But isn't church like this? I am a Protestant, Calvinist, amillennial, paedobaptist, and cessationist (though I'm open to God's mysterious ways). I'm on choir with people who speak in tongues, believe God tells them things outside the Bible, and people who generally believe whatever is popular. I go to a church who only baptizes professing believers, but thankfully they won't make me get rebaptized. People have been horrified to find out I'm a predestinarian, though in all reality, I believe they believe in it even though they don't realize it. But we all work toward a common goal: glorifying God and proclaiming the Gospel to children. Yes, I will work alongside people who don't truly believe. I certainly have emotional ups and downs with God at times. But Jesus put us all together and he's the one working, not us.