Who is Mr. Johnson from To Have and Have Not and what is their importance?

Mr. Johnson is the rich American who hires Morgan's boat for three weeks of fishing in the Gulf. An inept fisherman, Johnson hooks and loses three sailfish, fails to follow instructions, and also loses Morgan's expensive tackle and rod. Johnson dickers about the cost, but he agrees to pay after the bank opens in the morning. He flies out of Cuba, leaving Morgan in the lurch and forcing him to engage in illegal smuggling.