In his formative years, Dylan relied heavily upon traditional music for tunes and extracted some which were not on the tips of every would-be folk singers tongues. He had a good ear for tunes when he used them and could hold onto peoples's attention with his lyrics even though they did not always follow a logical path. As his skill developed, he became less dependent on tradition for tunes but continued to address themes of traditional music, ie the things that were going on around him. He could also tell a tale. It is fun to try to analyze his success, but the man had, as has been said several times already, a touch of genius.