A lot happens in that first chapter of Mark.
Forty days of temptation is summarized in 2 brief sentences. Jesus’ sermons are summarized in a single sentence: “The time is fulfilled, and the kingdom of God is at hand; repent and believe in the gospel.”
This makes me more than a bit curious. I find it hard to believe that He went around just proclaiming this one sentence. Yet, if He taught whole sermons, how many did He teach? What texts from the Old Testament did He use? How did it go with the audience when He proclaimed Himself as the central part of the sermon, as the Messiah, or did He in His teachings? Perhaps the biggest question of all: How did He tell people to repent and believe “the gospel” without having experienced the cross and the resurrection?
Surely someone knows the answer to this question.
So much happens in these chapters, it is nearly impossible to summarize in a short post. I will say this: the majority of things recorded seem like random tidbits of memory recorded as they came to the writer. Also, the majority of the events recorded were likely memorable because they were situations in which Jesus did something extraordinary–healing, casting out demons, challenging authorities, challenging traditions, giving stern warnings concerning an eternal sin, and choosing twelve disciples who were anything but extraordinary, that is, before Jesus got a hold of them.