There are three sections in today's gospel; the prophesy of the passion, the request by the sons of Zebedee and the question of Christian leadership.
In the 1st, Jesus is pointing out the cost of being a Christian. We will have troubles because we stand at odds to the world.
People, including some of Jesus' disciples will misunderstand what the Christian message is about and shall see it in worldly terms. This is human nature and Jesus will soon put us right when this arises.
Lastly, Jesus turns the whole idea of leadership on its head. For the Roman world, as for our world today, leadership brought privileges. It is not to be like this among the Christians.
The message of Jesus turns our worldly ideas upside down.