Jesus leaves Jericho on his way to Jerusalem. As Mark tells the story, nothing of importance happened in Jericho at that time. Jesus is focused on getting to Jerusalem for the showdown with the authorities of the Jewish establishment. He plans to reveal himself at last as the Christ, the long awaited savior, the "Son of David."
Mark has been careful so far to preserve this secret identity of Jesus. Anytime demons proclaimed his authority and divinity, Jesus silenced them. Those who were healed were often admonished to say nothing about it. It has only been very recently (Mark 8) that even the Twelve began to put things together and understand Jesus is "the Christ."
Why, then, does this blind beggar, Bartimaeus, already know that Jesus is "Son of David"? The answer directs us to know how to be faithful disciples in our own time when so many blind their eyes to the truth of Jesus.