Could you please help me understand the meaning of this quote? Does the writer mean to say that the leader has no companion and he is sort of cut off?
A man who wants to lead the orchestra must turn his back on the crowd.

Hi Tom

I might suggest that the sense is this:
To ensure that something is done well, you must focus on the task at hand.

I also get the sense that although you may be ignoring many people while focusing on a task, those people will benefit from your focus in the end.
Its quite simple.... If you want to take control and be the leader then you must not follow what the crowd is doing. In an orchestra the miestro or conductor is in charge of the band and he stands with his back against the audience (i.e. crowd). To lead is to do and direct. The audience behind you are following with the music that you are composing.