This story  is, in the most general terms, an epiphany. The god appears numinous, both frightening and fascinating  to the mortal. The frisson of a listener (for the hymn was surely oral whether or not it was in some way liturgical) experiencing a vicarious glimpse of the divine may have had something of the appeal of a science fiction or horror film today. The hymn has a handsome leading man, fast action, and impressive special effects, what with the cascading vines and materializing beasts, topped off with the sailors’ metamorphosis into dolphins.
Moros is sometimes translated fate, but, considering that Hesiod deemed moros “hateful,” perhaps doom is a better translation. As the parthenogenetic son of Night, Moros carries dark associations, but then the Moirai (Fates) themselves, though euphemistically called the Parcae (“Sparers”) in Latin, are described as ugly hags, closely associated with mortality and with death. Their worship arose in Mycenaean cult practice and, even in later times, they generally seem to operate independently of the Olympians. A dying and reborn god imported from barbarian realms, Dionysos is an appropriate partner for these archaic powers.
Further, the incident presents an illustration of the imponderable and sudden turns of the wheel of fortune. The captain is particularly brought low, the helmsman, who was treated with disrespect is elevated, and the crew, anticipating a routine voyage, are suddenly transformed in a moment.
In this hymn’s first line, the god’s semi-mortal origins are highlighted. He is the son of Semele (herself also semi-divine) who is herself undone by her encounter with the fully divine, though Dionysos later rescued her from the underworld just as he himself was reborn after being torn to pieces by Titans. The affinities to figures like Osiris, Adonis, Attis, Tammuz, Asclepius, and Orpheus are clear. Surely, these cults as well as the Mysteries and Christianity were imported by ancient Romans seeking personal salvation. Dionysos invites believers to identify with him, even to become him in rites of of enthusiasm and ecstatic possession.
In this poem, though, his divine omnipotence is stressed. Though taken for mortal, the theophany is a markedly extraordinary human. Dionysos is youthful, well-dressed, strong and sexy, consistent with his role as a fertility deity. He is long-haired and probably beardless, the sort of representation that might be associated with his epithet Androgunos (“androgynous”). He smiles (line 14) with profound confidence and works his will with cunning means.
The incident may be considered, like the story of Pentheus, as a cautionary simple tale of retributive justice. With Dionysos pulling the strings, a moral reading is certainly present. The greedy pirates are punished, their ringleader first of all, and the virtuous helmsman is blessed. The sailors had been interested in a ransom, preceded, perhaps, by a bit of fun, but they found their egos chopped for grabbiness. Even after the miracle of the bonds falling away, their selfishness blinds them to the god’s power. The captain is warned, but will not listen. Those who in the end suffer dire consequences for their actions are offered opportunities to reconsider, but they persist in error. Like the moral reading of tragedy this is true but reductive. 
When wine swamps the decks and an ambrosial scent arises, the men are paralyzed in awe. Foliage leaps forth from grapes and ivy, bursting with fruit and flowers in a wild excess of generative power, recalling other epithets of Dionysos: Phleon (luxuriant, said of foliage) and Auxites (giver of increase ). Then, however, the fierce beasts, the lion and bear, materialize, reminding the reader of the Dionysian predilection for homophagia, the eating of raw meat after sacrifice.  The vicious captain falls victim to the lion, while the crewmen become dolphins, animals regularly considered beneficent by the Greeks.  Their animal form then becomes a kind of purgatory where, by doing good services, they may expiate their guilt. Surely, these ordinary sailors bear a limited guilt, neither vicious like the captain nor as insightful and scrupulous as the helmsman. The latter appears as a sort of saving remnant, offering a better fate to the more pious individual.
Violent though it be, the tale lacks the macabre horror of Pentheus’ end, but the interlacing of death with life is tight and consistent in myth. Even the Ikarios story of the introduction of Dionysos’ gift of wine includes murder, suicide, merciless revenge and the founding of a propitiatory festival to placate the angry deity. Dionysos Lysios means the Undoer, recalling Dionysos’ literal “undoing” in his being eaten and the tragic hero’s cry “I am undone!” as well as implying the Liberator, the one who frees humankind. 
The poem concludes by noting that Dionysos’ aid is essential to the poet. Of course, the origins of the dithyramb, from which, according to Aristotle, tragedy developed were Dionysian, and all theater was offered to the god whose image was seated up front. For moderns, Dionysos corresponds to the unconscious from which arise metaphor and image. The worshipper’s loss of ego in the god is similar to the reader’s participation in the poet’s vision. And in modern times Dionysos has been the popular favorite in his contention with Apollo for the lyre. It is he to whom Nietzsche appeals for the punishment of his critics in his first dithyramb. 
1. References to the story also appear in Eur. (Cycl.11), Ovid (Met. iii. 582-691), Nonnus (Dion. xlv. 105-168). Briefer mentions in Apollodorus (iii. 5. 3), Hyginus (fab.134), poet. astron. ii. 17 (after the Naxica of Aglaosthenes), Seneca (Oed.449-466), and Nonnus (Dion. xliv. 240-249) Servius (on Verg. Aen.i. 67), Oppian (Hal. i. 650)]
2. The terms are Otto’s: mysterium tremendum, inspiring fear and trembling; and mysterium fascinans, the tendency to attract, fascinate and compel.
3. See my “Oedipus and the Meaning of Polysemy” (July 2011).
4. Dionysos is also called Aigobolos (goat-killer), Taurophagos (bull-eater), Bouphagos (cow-eater), Moschophagos (calf-eater), as well as Anthroporraistos (man-killer).
5. Apart from having rescued Arion, they were considered to guide ships. The very name of Delphi derives from Apollo’s arrival in dolphin form.
6. Still another of the god’s names is Eleuthereus (of freedom).
7. In “Dionysos Dithyrambs 1” Nietzsche describes being ridiculed as a foolish poet and imagines the “hot-hungry” god descending to avenge him by “tearing to pieces the god in man/ as well as the sheep in man,/ and laughing while tearing.”