Why is the conductor the most important part of the orchestra?
A conductor of an orchestra has many responsibilities. The primary responsibility of the conductor is to conduct. For example, they have control over many musical elements such as tempo, pace, etc. The orchestra depends on the conductor to make the musical piece flow as it should.
Conductors have many other very important responsibilities as well. They are often the "spokesperson" or public face of the orchestra. They must also be familiar with entire works of music and must know exactly what instruments need to be played at specific points throughout the piece. In addition, they sometimes choose which pieces are going to be played and often are an important part of the hiring process in regards to orchestra members.