Why is Captain Ahab obsessed with killing Moby Dick? What does Moby Dick symbolize ? Is the crew willing to help Captain Ahab?

Ahab wanted revenge against Moby Dick for taking his leg.

Moby Dick is a symbol of the power of the natural world, and the limitations of man.

The crew assists Ahab because they have to. Starbuck is the only member of the crew to openly oppose Captain Ahab.