Think of the monomyth (4.1). Jason's threshold crossing would be his dismemberment. The elixir theft would be his theft of the fleece. But, the narrative you read doesn't really emphasize these things. It emphasizes tests and helpers. Why? What is it about Jason that makes others quick to help him? Is it his looks (image)? His money? His character? His really big ship (image)? Some combination of these or other elements? Not even poor Heracles (image) had the kind of help Jason gets.
Jason does not rely upon himself alone to accomplish his quest for the Fleece. The key to Jason's success is his ability to delegate tasks to others and convince them to accomplish their task. I don't believe that he is successful in this endeavor because of any particular personal quality. The crew of the Argo simply understands that they all need to contribute something for them to accomplish the quest. For instance, no particular rhetorical skill or personal charm convinces the sons of Boreas to attack the harpies. They simply have the skills to do the job. "And it came to pass that, swift as the wind, the sons of Boreas rose to meet the Harpies" (177). Later, Medea would not have helped Jason if Aphrodite had not directed Eros to cause Medea to fall in love with Jason. "'Foam-born Aphrodite must have her son, Eros - whose love-inspiring arrows flood even the hearts of the Olympian gods with fear - aim his bow at King Aeetes' maiden daughter'" (178). Jason simply benefits from Hera's desire to punish Pelias.