Mark picks up, here and throughout his gospel, a major theme from the ancient Hebrew scriptures: that when Israel’s God acts in fulfillment of His ancient promises, He will do so in dramatic and radically new ways. Here, to be sure, is a paradox we meet throughout the New Testament: God acts completely unexpectedly–as He always said He would. Just because the new events are able to be seen as the fulfillment of ancient prophecy (and Mark, like the other evangelists, is clear that this is the only right way to see them), that doesn’t mean that one can see a smooth, easy line from the ancient texts to the modern fulfillment. On the contrary, what is being fulfilled is precisely the promise of drastic, unexpected, and perhaps even unwelcome judgment and mercy.
But our proper emphasis on this radical, new breaking in of God’s action in Jesus ought not to diminish the sense that, in Mark, this new thing that God is doing is the new thing He had always promised.
— N.T. Wright, How God Became King: The Forgotten Story of the Gospels, 75.