The theme of The Old Man and the Sea is never give up on goals in life , given time they can happen.
After 84 days without catching a fish he says- “the old man said. “I feel confident today.” Pg 6 If the old man had given up on his goal to catch a big fish, he never would have had the chance at catching that big marlin. Just like nobody else should give up on their goals in life.
He wrote the story to entertain and He wrote the story about an entertaining subject. It was entertaining by the descriptive writing he used to describe his fishing trip. And it was a very entertaining story.
His intended audience was fisherman. He talked in detail about how to fish and how he fished.